64 Chevy 3 spd tranny question

I need to replace the tranny in my 64 C-10. I bought a boneyard unit from a 57. Looks the same, but I just noticed the 2 lower bolt holes are not threaded like the original (bolts up from clutch side of bell housing). Will this work in my truck as long as I use longer bolts with nuts?

Sure it'll work. Trucks were odd those years, no real reason for the bolts being put in from the front. Some had all four that way.

Thanks!!........