I have a 73 z with a 550 horse 427, turbo 400 and a 12 bolt with 4.33 rear gears, the thing is I live an hour from anywhere, and am pretty much stuck in my little town because the thing revs at 3300 at 60mph, I am going to put in a manual transmission and new rear gears to get the revs down on the road, so my question is whats the better transmission to handle the power, the Muncie or t10, and what rear gears would be best so I could cruze down the highway under 2000 rpm, I will also be bringing my car to the strip a couple times in the summer bracket racing. thanks guys

 

Welcome aboard. I have similar power in my 72 and have had no problems with the st-10 but I have not had it at the track yet. I run a 3.42 gear and have a 17 inch tire that stands 26.5 inches iirc. At Roughly 2300 rpm Im doing about 60 mph 3000 rpm is about 70. That used to bug me a little but Ive become used to it. If you want to drop the revss to the levels you are talking you probably should go od.

 

Keep the rear gears you have and put in a Tremec TKO 500 or 600 5 speed overdrive. That will give you the best of both worlds; the good low end grunt like you have now, and a lower final rpm on the highway. The 500 & 600 is the torque rating.

 

I'd agree with going to a 5-6 speed trans if you're swapping to a stick. A 4 speed wont do anything to drop rpm's lower than a 3 speed automatic. Not sure how useful 1st gear will be in a TKO 500-600, as 1st gear ratios run in the 2.87 to 3.27 range. Might end up swapping rear gears anyway, but I'd start with just the OD trans swap, and see how that works.
I'm running a ST-10 4 speed behind my 464 BBC, with 3.73 gears, and 30" tall Hurst slicks. It cruises down the highway around 2300 rpm at 55 mph.