Question about 51 Chevy Fleetline

There's all kinds of aftermarket parts you can get to either build your own killer power plant or a ready made just drop it in one (Ross Gibson Engines). It all depends on how much you want to spend, just in real life LOL.

Here's a link to help get you started - Detail Masters.

There's a couple of ways you can go about lowering the rearend.

Use heat and re-arch the springs (flatten them out) until you get the desired height. I've held it over the heat of a candle with needle nose pliers on each end, just until I could feel it give. Don't get too close or it will burn. Then you'll probably have to relocate or rework the shackles. The ends of the springs will now attach to the frame further away than before as the springs will have gotten a tad longer.

Carefully remove (cut) the axle from the springs. Add a spacer block between the two and reglue. Problem with this approach, the springs will be dragging closer to the ground.

The easiest, is to cut the shackles shorter if there's enough there to allow that, but probably not. You can also file away some of the frame where the springs (shackles) attach, get glued on.

Depending on how much you want to lower it, maybe a "little" of all the above to get just the right look with out overly distorting the look of the springs.

Gee... I miss that little alcohol burner that came in my chemistry kit when I was a kid. 

Good luck and have fun.