I would go talk to an A/C expert.

 

The 12a's use a compresser that both hoses connect to the compresser with one bolt. The 13b (GSL-SE)'s compresser uses seperate hoses. each hose connects to the compresser. I agree if you change the whole system over,,then maybe so. The condenser and the fitting at the firewall use the same size thread. just change the compresser and hoses, and maybe brackets.

 

Sounds Fun and Rewarding!