I thought the 366 truck motors were different than the reg mark iv bbc...but i don't know.

you have a 4 bolt main capped motor.i dont know how big you can bore your motor out to,but ive heard that the old 366 and 427 truck blocks can get up to 4.375" SOMETIMES.i would sonic test it after it gets opened up to common 454 size of 4.250".it is not a total loss for all that youd have to do is pay a little more for a bore job.