Hi there i have a 69 firebird in restoration
now i have an ls1 out of gto for good price that im thinking on puting in with 383 fordge internal going for 11.x compration and a camshaft with good street idle around 560 lift
Going to stay with the 241 heads or an lq9s heads until i get some ported 243
Looking to get 500 engine hp at the start
And 550 to the wheels with the 243 and nosIs 500 engine hp posible without the 243 and super big cam?
Other then that a t56 and ford 8.8 3.73 31 spline

 

Do NOT use the LQ9 heads (317) unless you want to lose a TON of compression. They have 71cc chambers compared to 67cc (241) and 65cc (243/799).

 

Agreed 243 will put you at 10.5:1 compared to 10.25:1 stock ls1 heads the other will put you in the 9s great if your wanting to boost it. 243 milled .030 will get you close to 11:1 and we’ll over 11:1 with 383 stroker. 550 is not impossible but might take more than just 383 heads and cam especially thru an auto.