Sorry for the delay in replying, fuelie. My Elky came from the factory with the 325 hp version of the 396. However, a bit of motor magic has transformed her into a more respectable 422 HP......................Ken
It's a '68. It came out with the mild version, but it is somewhat wilder now - approx. 400 HP. Runs very well for a classic. If you're interested, Go to the MuscleCar home page where you can view past shows. Select the Blue Collar Buick Tail Light show, and my Elky was the feature car on that TV show.
you can use the big bore heads on most small bore blocks but that usualy leads to detonation&lower cr witch =less power& torque.it,s best to stay with heads made for the same bore.hp 305's would work but they got the bolts in the ends and dont look like th old stuff.if you have some of the old heads just rebuild them,bronze liners,stainless biger valves,pocket work to match the valves,harder ex seats may be nessary,I have hardened seats with acetylene torch before, but thats kinda tuchey & would not recomend it., good luck and have fun,dont get hurt having too much fun(thats when you get cought)