Motor mounts are no problem.  The donut size on the exhaust is different if I am remembering correctly....and BB exhaust manifolds re notorious for cracking.   Certain years of pickup frames have to be notched slightly to clear the big block....I think this only applies to a few model years where there was no big block offered.  The bellhousing and flex plate  will bolt right up.    It will probably need more front suspension. 

We built a 454 at about 10.7:1 a number of years ago for propane.  It's a strong pulling truck...ultimate hp (at high RPM) is limted by the smallish IMPCO carb but it pulls good at lower speeds.  The high compression will be a big benefit and you would also benefit from as much lift as you can get on the camshaft along with fairly stout duration.  We used 12.5 dome pistons with large chamber heads to get the mentioned CR.  I was advised that the large chamber heads flow better then the smaller ones.