My 16 year old son recently purchased a 1984 firebird 5 speed 305 H code with a rod knock. I found a rebuilt long block from a 86 but I understand that my car is the old two piece rear main seal block and have 86 is a one piece. I'm a ford guy so this is all new to me. Can I use this block? Please advise

 

can use the '86 block- but will need to use '86-up flywheel because crank end is external balance and bolt pattern is different.

 

Yes you can use it. You can just go to autozone and order a 1986 305 V8 Firebird / camaro 5 speed flywheel and you are good to go. I believe the starter is the same.

The transmission will bolt up just fine same with the heads. The cam you will want to replace I would not swap a flat tappet between motors go fresh and break in properly per manufacturers instructions.

 

Yup; starter is the same, clutch is the same, bell housing is the same. Only thing you have to change, is the flywheel.

Personally, I think it'd be kinda short-sighted NOT to replace the clutch at the same time, especially on a freshly purchased (i.e. unknown condition) car; but that's just me. Costs pennies, might save MAJOR aggravation acoupla weeks on down the road.