Question about 48 & 49 Chevy Trucks.

[Ltcrazyx]

I currently have a 48 Chevy Thriftmaster with a very bad body. I found possibly another Thriftmaster but it's a 49. I want to start working on the frame of my 48 right now and get it all prepared and such. The reason I can't just use the 49 is because I won't be able to get the truck till more then likely october. What I was wondering witch I already more then likely know is can I use the body off the 49 on the 48. Now the main diffrence I have noticed is that the 48 has the gas tank underneath the truck where the 49 has it behind the seat. I would like to keep it under the frame so what I was wondering would a 48 frame work with the 49 body parts. Also I was wondering if people had links of trucks being built for these two trucks. I was also thinking bout as I said before making the tank stay underneath the truck can I just fill the whole where the tank is or is the cabs that much diffrent?