the difference between the pontiac 360 hp and 370 hp 70 455 was the heads,#15's had small valves and pressed studs,#64's had big valves and screw in studs,the valve size alone is more hp.Plus the gto version you could get the 068 cam with a manual trans,again more power over the 360 hp version.Plus all the gto /gp 370 version came with 4 bolt main caps.I bought my 70 455 4 speed bone stock.I tried it at the track a few times and had someone mention to recurve the dist.He helped me do it at that time,(20 years ago)and i remember taking the original advance springs out,they had so much tension,i had to use pliers and pull hard to get them off.(i still have the originals)He told me he couldnt see how the thing would ever total advance.It knocked a few TENTHS just redoing the dist.,something they should have done better at the factory.Ran mid 13's pretty well stock.
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