How to I.D. subframe ?

I am trying to i.d. the sub frame in my 68 nova.I swopt subs a while back. The one I installed fit pretty well except for a few things. It did not have the extra hole for the bumper, no holes for the turbo 400 crossmember, and if I remember correctly my original sm. block frame mounts would not align with my original motor mounts when I first did the swop.
If anyone can help me sort this out I would greatley appreciate it.