I know I am going to need a 10J rim to be able to use these. My question is what offset do you think I will need to be able to shoehorn in these rubbers to my stock rear fenderwell. Or am i hoping for the impossible?

 

I have an eastwood fender roller you can rent. PM me if you want it.

 

will depend on the physical footprint of the tire - the # on the sidewall really doesn't mean much. On a 10 inch wide wheel, something in the high 20's to high 30's, roughly, if it's a tire that has a very broad shoulder