Hi Mel, welcome to Stovebolt. I am a big fan of the sixes in these trucks, but yours very well may have had a small block in it when new. I am also an even bigger fan of the big blocks, I have 2 cars with BBC engines a 396 and a 454 LS6. Can your truck handle 500 foot pounds of torque? Nice to have a few options, have fun!

Leo