Vintage Powerglide transmission info. needed

[JHS]

I have a cast iron Powerglide 2 spd tranny that is in excellent condition. It weighs a ton and must have some use for either a '55-'56 chevy resto or??? Someone told me these units are being reworked for drag racing but seems like the weight would be a problem. Anyone know what this thing might be worth and how I can identify it's application and year of production? I do not see any dates anywhere.