Help with new engine decision

If you like the motorhome and you can rebuild the engine yourself, do it. You can easily rebuild that 454 for probably $1500 if you do all the work yourself. Getting it out should not be that bad if you have a driver's door. Take out the driver's seat and rent a good sized cherry picker to get 'er out of there. Break it down and have a machine shop do the bottom end, you do the top end, or maybe just do it all yourself(minus the machine/bore work). You always want to go .030 overbore and new pistons. Have the heads ported and go with a different intake if you want more power. It's always gonna be a big block gas engine, not a diesel powerhouse. My '94 P30 with the 454 isn't exactly a tireburner either, but it gets around ok for the size of the rig.