PRO 3 is not actually a BMW CCA Club Racing Class, it's a regional thing in the Pac NW.

If they ran in the BMW club they would go in that org's KS, or K-Sport class.

my understanding is - gut the car, can't open the engine. you can play with shocks. DOT ri In other words, they would be back markers in ITS and extremely far from competitive in STU - but they should be eligible for STU and be able to participate in the Majors/Super Tours/Runoffs.

I would plug them in under the STU alternate vehicle allowances table and let them run at 2650# under their Pro3 rules except that tire brand would not be restricted, and of course they have to meet STU safety requirements like dash bars.