Talk with GPSE3400 over on 60degreev6.com. He had done two cars with a 3400, 89 gpse and a 92 DOHC SE both were refit if 3400s. He can also tell you how to build the engine with crazy 12:1 compression if you want

One of the most knowledgeable guys I know on this subject.
BTW see sig....he also helped me put the 3400 on my girlfriends 97 skylark GS.
Ken