The powerglide and tall gears make that a bit more of a challenge than one might think...
Time for a 4l60e (3.06 1st gear) ... if the rear gears are really numerically low - run the trans in drive and lockup. It'll make a big difference how the car runs. Get a trans out of a '98 ish astro van. The drive shaft "might" need to be shortened. I can supply a simple shift controller from PCS.
Others here may whine about the gear ratios in them but I have run them for >15 years and like them.
