77 motorhome 440 vs 71 360-what to use???

Hey guys....so here's some background on what i have, what i'd like to have and i'm all ears for any opinions and comments on the matter:)

I have a 70' duster, factory slant six car and also have 2 engines here, both complete NEVER torn apart.
(1)71' 360 with 727A
(2)77 440 with 727 from a Coachmen motorhome

In the long run, i want my car to handle relatively well (keep up with base model challengers at least) and be comfortable on the highway and have a minimum of 400hp naturally aspirated. Since i'm starting from scratch either way since EVERYTHING in the drive line will have to be replaced, i just wanted some general feedback on what you guys would do??? It just seems so much cheaper to build a big block with good power than a small block with equivalent numbers and now that Procomp has aluminum heads for BB's for $450, i could shed some weight and not break the bank. My budget is about $3500-$4000 for either motor, 727 auto for either, 3.91 gears....keep in mind both are complete. Perhaps somebody can shed light as to some PROS AND CONS OF A MOTORHOME BB AS I KNOW NOTHING ABOUT THEM. Thanks in advance, you guys are great! -Dan