old truck enthusiast

[72 Unlimited Camping]

HI, I'm new to this forum and posting all together.
I have a '72 GMC Sierra grande 3/4 ton 2WD that i've been working on and using as a daily driver since 1995. It has a 350 w/400TH.
I am an outdoorsman so we are using the truck to go camping, hunting and fishing all the time. It must be able to run the freeways and backwoods.
A few months ago we bought a '79 Lance camper that weighs 2160 lb dry.
The 350 that is in the truck is tired and barely makes it over even small grades.

The suspension has all been udated over the years with the intention of caring a load. I may still have to add air bags thou and will eventually need advice on this.
Right now I am deciding on putting a 454 BB in. I have the motor that needs to be rebuilt. (its stripped and ready to go.) or just rebuild the 350 that is in it now. The original motor for this truck was a 400ci with dealer code L47.

My question is how difficult will it be to swap over to the 454? does the driveline need to be altered? ( I have the 2 pc driveline). will the tranny move back? how about radiator in/out position etc. I'm not afraid to tackle this stuff just need to now what to expect so I may budget my resources. If it is just as simple as using new mounts than great. Somehow I doubt it.
Thanks,
Tony