I think you got the right idea, start finding parts and wait untill you have everything then have it done, or research the job and do it yourself. When looking at trannies be carefull for old junk that is weak and obsolete. For example, you will find T-10's that look great, but are from the 50's and not worth a crap. Saginaws come with anything from 2:56 to 3:11 to 3:50 first gears. I had a 3:11 first gear Saginaw behind a 400 GTO motor and 3:23 gears out back that was a total ball to drive, and never gave up. The Super T-10's are way better, even better than the Muncies they replaced. Also most Muncies are from the "Muscle Car" age and have like 2:21 first gears. Great for racing, but for a highway cruiser, later ST-10 models came with very low first gears that you can use with low highway gears for the best of both worlds. My aluminum ST-10 is an 82' with 3:42 first, and I have it in my 77' TA with 3:08 rears. My wagon has a Saginaw with 3:50 first and 2:78 rear, it gets 20 mpg with a 301 V-8. I call that my "poor man's overdrive".I have no knowledge of 5/6 speeds to share but many on this site do and will be glad to educate you. So take the winter to research and decide what you want so in the Spring when swap meets start up you will be armed with the right information.