IF I WAS YOU TO FIGURE YOUR RPM AT THE TOP END FORMULA IS THIS.....MULTIPLY 336XGEARXWHAT MPH YOULL MAX OUT AT THEN DIVIDE BY TIRE DIAMETER...EX,100MPH TIMES 336 TIMES 4.10(REAR GEAR RATIO) DIVIDE BY TIRE DIA OF 29 INCHES=4750 ADD IN A LITTLE CONVERTER SLIPPAGE DEPENDING ON IF ITS TIGHT OR SLOPPY,5% IS ABOUT AVERAGE.......TOTAL=4987.5 RPMS@100 MPH!!!
AS FAR AS POWERGLIDE DONT KNOW,SHOULD BE MORE CONSISTANT THAN TURBO TRANNY,BUT A STOCK T400 IN STOCK FORM SHOULD HOLD UP NO PROBLEM,AND WILL BE A LIL TORQUEYER CAUSE OF MORE GEARS...GOOD LUCK,ID PUT A T400 IN IF IT WAS ME!!!