1964 Chevy C10 Questions

At this moment I only have two questions:

1) Is there a 5-speed trans that will bolt onto my 292 straight six motor?
2) What is the disadvantages to cutting off my muffler?

Thanks in advanced for all the help.

1. No factory but I think there was an aftermarket. Check preformace catalogs. I don't know if they are still made.
2. Police and carbon monxide.

it is ok to remove your muffler... but you have to keep in mind that if your pipes are to short you will not have heat built up in there and the engine can suck cool air back into the exaust chambers resulting in burnt valves.