The mounts may be different but I am fairly sure you can do the V-8 swap by re-drilling either the 6 or V-8 mounts that attach to the engine. I did this to my 59 1/2 ton in 1976 while on a summer job away from home. My tired old 6 left smoke that looked like a fog bank every time I hit the throttle after decelerating. The only engine I could find was a 327 from a wrecking yard. My brain was a little "fogged" too back then so I can't remember the details but I know I did it and without any purchased parts beyond what I got at the wrecking yard.
Chuck
