Like Trip said if the donor is a 5.0 then you'll be fine BUT if it was me going the trouble I'd start with fresh parts. 70,000 miles doesn't sound like alot but if it's a stock part on there... might have had a hard life. 
__________________ 66 Coupe Tahoe Turq - 200, Pertronix & Flamethrower, 3 Row Rad, Cliff. 6/2
96 GT Vert Laser Red - FMS pulleys, Bullet ProM, BBK CAI, Prof. Prod. Elbow and 70mm TB, MAC Off-Road H, Borla side exhaust, Tokicos, B&M Ripper, 18x10 & 18x9 DD Bulletts
06 GT Tungsten, UIP, Red Leather, Stick, 18" blades, Steeda CAI, SCT XCal 2 w/ MC Racing 91 tune, MACs, BMR SP010 springs, BMR Adj Panhard, CDC ducktail & quarter louvers, Rear louver, painted black stripes | 
Shock Swap need help 
