Chevy & GMC Vans

I recently bought the swivel bases you see pictured here at a yard sale. The guy didn't know anything at all about them, such as what they were made to fit, what they had been installed in, or how the top plate was supposed to be oriented to the bottom plate when in the locked (as in when in motion) position. Fortunately the bases were marked, apparently from the factory (made in Taiwan) with a "DD" and a "DP".
Using that as a starting point, I moved the top of both bases into the locked position, under the assumption that the side of the base that the handles pointed to was probably the front of the base.
The two pictures with 2 bases in them show that in the locked position, the cylinder that supports the bases is positioned (welded) slightly toward the front of the bottom plate, and slightly to the middle of the van. I'm guessing that the offsets are about 2 or 3 inches each. In other posts I've read on the subject, it has been mentioned that this was necessary to be able to rotate the bases clockwise without hitting the door frame.
If you look at the picture with the passenger base sitting in the passenger side of the van, you'll notice that the four corners of the base plate each touch one of the factory seat bolts. The following are some areas I'm looking for input on.
Any suggestions on how to attach these to the floor? The idea of drilling through the van floor at the existing base holes doesn't appeal to me as each of these is directly over a fold in the van floor (to create the dips in the floor for the factory bases). I'm thinking that about 4 inch strips of 1/8 steel cut into strips, and welded across the two rear holes, then again across the two front holes, then drilled out to take the factory bolts would be the strongest and simplest way to accomplish this. I'm just not sure how to get the welded strips to conform with the recessed bolts.
As to mounting the slides to the seats, I have 2 concerns. One is, I suspect that the GM slides are preferable to the Taiwan slides, but can't figure out how to separate them from the factory bases and mount them to the swivel top plates.
The main problem is how to attach the slides to the seats. I'm thinking maybe using a plate of 1/8 steel spanning the underside of the two buckets, drilled out to accommodate the bolt holes on the seat bottoms and the slide bolts.
I've also noticed that other posts refer to the matter of the factory seats being positioned so that the seats are tilted. Any suggestions on how to accomplish this? Would using a stack of washers be too crude?
Any help that you guys can offer to resolve these issue, or any issues I may have overlooked, would be massively appreciated.
Thanks guys.
John B.

Those look really narrow, tall and offset. I would think that you are going to have to modify them pretty extensively to get them to work for what you want.

I was thinking about trimming the length of the aftermarket floor base, then overlapping it on both ends with about a 4" wide strap drilled and bent to accommodate the factory screws, then welded together.
As for the seat attachment, there's no way the swivel base holes will line up with the stock seat holes. I also can't use the factory base together with the aftermarket base. Way too much height, unless I separated the stock slides somehow and found a way to mount them to a plate drilled to line up with the holes in the bottom of the seats. I'm also thinking that I will have to use the aftermarket slides screwed to a larger plate which would, in turn, be drilled and bolted to the bottom of the seats. This doesn't address the problem of trying to replicate the tilt of the stock base, however. Stacks of washers maybe?

I think I would just bolt the pedestal to the floor as designed, add a 3/8" plate to the top and bolt to the top of the pedestal, then add my seat and sliders to that plate. If the is too high then the plate will need drop down edges for the sliders to attach to. (-L).

You should get the tilt from your stock sliders and frame, if that's too tall, take the sliders off the bracket and attach directly to the plate. You can also use washers above the plate, unless you want a tilt-a-whirl ride.

Also, check the bearing ring for a tight fit, those are rather cheap bearing and as they wear the seat will become a rocking chair. That's annoying!

OP, any update?
I just tonight pulled the front passenger seat and going through the head scratch phase as to which swivel I will use.
One looks much like yours and is from a full size Chevy van. The other is a CL find of unknown history.

Hey guys this look a lot like mine. Here was my solution for using the swivels and getting around the heater duct. The following is from page 3 of my build plus a few extra pictures attached.

Snowgeek wrote:It has been a really busy year and I have used my van camping and during bike races but haven't made to many mods till recently.

I had a customer get out of his ambo-camper and walk into the shop. After talking for a while turns out that he had a pair of astro seat swivels that he wasn't using. The passenger swivel was designed for a floor board with out the heater ducts so I used part of a stock base.

Drilled out the bolt holes to allow the bolts to pass through



Nestled the base into the cut down stock base





Fabing the extensions that will be a wide enough mounting point for the land rover seats.



Seat now swiveled



I do have more pics if any one needs them, just let me know.

Ryan