i am gathering parts so i can do my conversion soon after the first of the year. a guy i know has a set of thunderstorm heads for sale CHEAP . i just want to make sure they will fit my 89 model. what about head breather vs. case breather issues? anything else i might need to know about before i buy them. thanks


anybody have comments?

Not sure but someone might know.

Gazza

Yeah they should fit, but you will have to modify the motor mount, just need to ream it out from a 3/8ths to a 7/16th I think. I just got a pair myself to go on my 97.

The pushrod spacing on a 4-speed is different. You may have pushrod rub issues. That said, a lot of people have put 5-speed heads onto 4-speeds.

The venting issue is your choice. You can either also update the lower and middle rocker boxes, and vent out the heads, or simply plug the head breather holes and continue to vent out the cam box.