Trouble removing pulley from power steering pump

Hi all, This truck ('89 Dakota 3.9L) came without a power steering pump so being on a budget I decided to buy a used one and install it myself. First problem: The used one came with a serpentine pulley and I need a V belt type. I have a replacement V belt pulley, but I cant remove the old one. It has an Allen bolt .at the center of the pulley facing in. I put the pulley in a vise and it is a 3/8" Allen drive. I tried a 3/8" air drive, but that didn't budge it. I have an Allen wrench so I put that in and even using a 4 foot persuader I couldn't move it. I sprayed it with Blaster penetrating oil and let it sit overnight but that didn't help. I could apply heat or I could drill it out, but I thought I would ask you guys before I make a mistake. Thanks for any Ideas. Regards
Author: okrobie