SCCA and NASA car classing question

I wasn't sure where to ask, so I figured this group would be the best place to start.

We're building a road racer out of an old stock car, and were wondering what classes we should be looking at in each of the rule books.

The car is currently bodied as a Dodge Intrepid, built for Sportsman/Late Model racing, and it's likely to end up with an upgraded 6.0L LS-type truck motor.

Thanks in advance.

GT1/SPO, WRL also has a class called GTO

For NASA, It'll be in some branch of Super Touring, likely ST1 if I remember right.  There was a guy competing an older stock car back in TX, I think it was in ST1.  Either that or SU if you don't dyno it.

I think SCCA would be GTO,  GT over 2.5 liter.

correction....   SCCA SPO  Special production over 2.5 liter  SPU is special production under 2.5 liter.   Or maybe GT1.

    I have seen cars like yours run SCCA.

Thanks for the help. Now I know where to go with the build in regard to rules. Based on limited budget, it'll be horribly uncompetitive in GT1, but I think SPO or ST1 is probably my best bet.