JiMerit, Do you have any pictures of your motor? I have what I believe to be a 53 Powerglide block. It has a stamping that reads:
LAQ4269I9. I have been told that the LAQ means it is a 53 PG car motor made in the Tonowanda plant. I just haven't been able to spot the casting number which should be in front and below the distributor.

http://www.picturetrail.com/gallery/view?p=999&gid=9706179&uid=1946755&members=1