my ohc motor appears straight, but the th400 crossmember i used was offset, so i had to cut, extend, and weld the mount pad.
the th400crossmember mount pad is offset similar to this Camaro BB 4spd crossmember, though it looks different. th400 is tubular and the mount pad is an extension. sorry, no pics of it.
Top/rusty is regular X-member, bottom is BB4spd x-member. these pics were borrowed from the camaro tech site.