I have a 454 I got for a trade recently and am going to drop this into my 77 camaro, but I'm still trying to figure out what it is.? -Block number is 3963512 -Vin number is T1008CGU -Partial Vin is 10R1153 Here is where I'm very confused, drive head is a 336781 head dated "D 7 76" but the passenger head is a 353049 head dated "F 21 78". Both heads stamped "pass" for passenger car. This block is all kinds of Frankenstein to me and I haven't taken heads off yet to see pistons. Ideally I'd like to drop this into my car with maybe just a cam swap and possible springs and rockers but now that this thing has different heads i don't know what to do.? Someone please chime in thank you and God bless!!