So what happens if you keep the old /6 rear end after 360 swap?

i have the december issue of mopar muscle and ther is a guy andy burleson running a 10.668 with an 8 1/4 ill post his stats

BLOCK: .030-inch over 340
CRANK: stock 3.31-inch stroke
RODS:eagle i-ibeam 6.123-inch
PISTONS:SRP 9.8:1
CAM: comp solid .540/.549-inch lift; 252/256 degrees duration at .050-inch lift
HEADS: edelbrock RPM ported by hughes engines
INDUCTION: victor 340 intake and carb shop 750 holley
EXHAUST: TTI headers with 3-inch pipe and flowmaster mufflers
ADD-ON: 150 shot of nitrous

TRANS: 727
CONVERTER: PTC 9 1/2 inch
SHIFTER: hurst promatic 2
VALVE BODY: stock

SUSPENSION

REAR: 8 1/4 with a strange spool and mono-leaf springs and cal-tracs
GEARS: 4.10
FRONT: factory k-frame with disc brakes
CAR WEIGHT: 3,300 lbs

BEST PASS

LAUNCH RPM: 4,000
60 FT: 1.60
SHIFT POINT: 7,200 !!!!
EIGHTH-MILE: 6.804 @ 102.83 MPH
QUARTER-MILE: 10.668 @ 126.39
* USING A 150 SHOT OF NITROUS