Well 8 valve cover bolts.... would suggest you don't have a 351W as long as it's not a "Clevor" (351W block with 351C heads) but lets keep it simple. The 351W has 6 bolts and the 351C has 8. As far as 351C goes?? The upper radiator hose should go into the block. The 351W goes into the intake manifold. As far as anything bigger than that... i don't know that much about them!! Someone will come through for you!! These guys are the best people on the net when it comes to your Classic CAT!! I noticed that you've got a 1968.... The 351 engines weren't produced until 1969!! Are you sure it doesn't have the original engine in there?? Check the door tag!! On there will be lots of info about your cat, engine, trans, interior type/colour,exterior color, model. A letter is what your looking for.... the only one i can remember off the top of my head is F = 302 2v
See what your says!! Then you will need to check the engine block to see if it matches.
If you know this isn't the original engine then you may need to get codes off items such as the block....... also if it has the stock intake, you should be able to get the approximate date of birth.
i.e If the intake cast date is 1968 it can't be a 351W or 351C.
Hope this helps a little!!
Just make sure you get GT heads or you will need them machined for the extra exhaust stud. to clear the shock towers
I gave $200 for my replacement out of a (WRECKED) 69 GT Ranchero. 16 holes for studs each head (some GT's only have 12 holes each head)
Good luck with the hipo rocker rails-they are worth gold in Dallas TX.