[rhino33]

http://www.hotrodders.com/kb/
this is a great site for running numbers

[lester]

you really need the year to, and the casting #'s on the back right side of the block. the YB was used for several motors
but being a 77 you really hope for a W72 400 with the Y6 or WA code .
from 77 - 79 the W72 400 was the icing on the cake. other then finding a SE

really look at your block code, make sure it's not a Y6 , some times it will look like YG

if its a 455, 455 will be cast into the left side of the block, beside the fuel pump