My '51 is all original except for the '60 235 running it. It's 3 on the tree with torque tube. I want leave it original but it is so low geared it will only do about 50 MPH flat out.
Its there an cost efficient option other than replacing the rearend from an S-10 or something?
I see Classic Parts has gears... is this it?
Unless you can cheaply buy a more-modern (and higher speed) used transmission and rear end, AND, unless you are able to do the adaptation and fabrication yourself, the 3.55 upgrade is a good way of getting moderately higher speeds.
Consider buying the installation kit. Also, consider calling
Patrick Dyke at Patrick's Antique Cars & Trucks (he is the source of those kits, sold by Classic Parts and others). Tell him your read about his 3.55 conversion on Stovebolt.com - ask him if he gives a discount (he usually will).
Also, ask him if the parts you want to order are in stock - when he runs out, all the 3.55 vendors have to wait for him to get them made and restocked.