I sold my 91 regular cab a little while back, I am 6'5 and it was just a little too small for my needs! I was looking for an extended cab for about a month, finally 1 popped up locally for 500 bucks! I ended up paying 450, but it was pouring smoke out the tail pipe. The interior, aside from the not stock carpet, and rips in the seats was in excellent shape.
this is what it looked like, you can still see my old regular cab in next to it! (the person who bought my truck was not able to pick it up for a while after the purchase))
here is after pulling the head
then deciding to just do a full rebuild