i have two sets of heads too pick from they both are stock( i think) but both sets have a different exhaust manifold bold pattern...one set has 2 bolt holes per exhaust port and on the other set 1 of the ports...(rear on the passenger and front on the driver side)...has an extra bolt hole tapped out just like all the other 350 heads i've seen...i was wondering if the set with just 2 bolt holes for each port is a special head or if it has smaller combustion chambers than the other head... thankx for n e input

 

After a certain year (87+ I believe) they came with the extra hole. Could be 350 or 305 heads. Check casting number here for original application:

http://www.mortec.com/castnum.htm

 

i don't think thats right cause i have a stock 83 truck with the extra bolt hole so that was the whole deal... which would make more power on my car because i have both kind and was wondering specs or age? thanks tho man