Have a 1992 Chevrolet caprice with original 15" wheels. Anyone know the wheel offset of the stock 15" rims?

I can't tell you, but here are links I'd bookmarked when learning when to how to measure what you need to for new wheel fit:

http://www.skulte.com/adapterfaq.html

http://customwheelsmarket.com/higperwheel1.html

http://www.rsracing.com/tech-wheel.html

http://www.edmunds.com/ownership/tires/articles/46431/article.html

I'm trying to figure out if I can put the stock Imapla 17' 8.5 inch rims with tires on my caprice and not rub the back rear well?

I'm trying to figure out if I can put the stock Imapla 17' 8.5 inch rims with tires on my caprice and not rub the back rear well?

Those wheels were designed to clear the caliper on the rear disk brakes (the 9C1 wheels were changed to accomodate this as well) so I suppose they will fit, but I can't be totally sure.

There have been owners of 91-92 Caprice sedans that have used the 94-96 Impala SS wheels before. There are plenty of pix on the web to prove it. They should fit but you might need to finesse them past the wheel skirts and the clearance on either side will depend on how centered the rear axle is in relation to the body. Check out one of the other Caprice/Impala web sites and do a search to find an owner that has them installed. HTH.