What is the lug pattern on a 1990 Caprice?

What else shares the same pattern, is it a common size among full size chevy cars?

Is it a wagon or 9C1 car or a civilian car?

wagon and 9C1s = 5x5" = pretty much any same era GM Fullsize truck
civilian car = 5x4.75" = pretty much any same era GM car.

Your 91 was the year they switched to 5x5 for all Caprices.

You post confuses me, do or do not all the caprices in 91 have 5 on 5?

btw: Mine is a civie.

You post confuses me, do or do not all the caprices in 91 have 5 on 5?

btw: Mine is a civie.

Yes, the '91-'96 cars put on about 600 pounds over the boxies (4200 lbs vs 3600 for my '88), and as such they gave all the cars the 5 on 5 pattern beginning with '91.

Prior to that, only the 9C1 and wagons had the 5 on 5, but the wagon axles won't work properly in the standard coupe/sedans.

Also, keep in mind that the wheel bolt pattern is not synonymous with the carrier size (7.5 or 8.5).

the wagon axles won't work properly in the standard coupe/sedans.

Why is that? So you better get the whole rearend out of a wagon if that's your donor car?

Well I guess I have the 5 on 5 then. Thanks everyone.

Why is that? So you better get the whole rearend out of a wagon if that's your donor car?

The mounts and shock points are a little different as it was explained to me. I've not tried it but CD Smalley certainly has the goods on it.

The track or overall width of the wagon rears is about an inch wider is the problem. The whole rearend itself would bolt up I believe. But the axles will not interchange between sedans/coupes and wagons.

aboveandbeyond - your original post asked about 90 models, while you say you have a 91. That's why I broke it down as I did.

OH MY GOSH!!
Good catch, I do have a 1991, sheesh I am sorry guys.

OK so I have the 5 on 5, got it.

Now I only wonder if I should still try to find a rear end with the gears i want and swap the whole rear end, or if would be more cost effective to just swap out the gears?

Doesn't that require special tools and so forth?

What do you think a shop would install gears for?

Swapping gears I personally would leave to someone who does it all the time, not just someone who has done it before.