Suspension and tire questions

[1974ChevyC10]

ok ol red will need new tires when i put the truck rally's on her.currently the rally's have bald goodyear wranger 31x10.5r15's on it.i will be replacing them with p255/70/r15's.i looked on tirerack.com and in that size they list the following tires
Kumho Road Venture APT KL51 (Highway All-Season)-87 per tire
Firestone Firehawk Indy 500 (Performance All-Season)-89 per tire
BFGoodrich Radial T/A (Performance All-Season)-93 per tire
Firestone Destination LE (Highway All-Season)-93 per tire
General Grabber HTS (Highway All-Season) -102 per tire
Continental CrossContact LX (Crossover/SUV Touring All-Season)-104 per tire
Goodyear Eagle GT II (Performance All-Season)-110 per tire
Pirelli Scorpion STR A (Highway All-Season)-248 per tire

i checked locally on this size tire and i know its kind of an oddball size tire alot of places would have to special order them i have yet to call discount tires or big o directly as for some reason i always feel like i lost 10 I.Q points whenever i call them about tires.most places ive talked to locally have quoted about 470 dollars including tires,mount,balance,road hazard,valve stems and all other taxes and fees.so tire wise do ya all think i would be better off getting them local or mail order them and have em mounted later.if i end up going the mail order route is there anything i can store to keep the tires in good shape in the event there in storage for a long time aside from keeping them out of direct sunlight and near anything sharp.also im considering lowering ol red 2 maybe 2 1/2 inches in front and 4 maybe 4 1/2 inches in the rear and what would you all suggest is the best way to achieve that height.im considering this because due to medical problems my knees from time to time give me problems along with my back and it would getting in and out of the truck alot easier for me but not as troublesome as getting in and out of my car can be for me due to its really low height.any opinions on both subjects are welcome.