273 to 383 swap

i've done many B body swaps from 273 to 383 or 440, now i'm going to do a 67 Barracuda 273 to 383. the previous swaps were to pull the 273 with stock mounts out, then put the 440 with stock mounts in (no modifications). now i know that the 383 with stock mounts will bolt to the k frame that i've just pulled the 273 out of (aside from various clearance issues such as headers, p.s, etc.). so what i need to know is what do the various motor mount kits do (Schumacher, Transadapt, etc) if the original mounts already bolt-up? do they shift the motor one way or another to allow p.s., or are they just new stock mounts? thanks for your help Gerry