Thats the T5. If you want a T5, you would be best suited to having a hybrid T5; V8 camaro guts, S10 mainshaft and S10 tailhousing. The proper S10 tailhsg and mainshaft for this conversion will have the mechanical speedo, and the shifter position is conducive to a bench seat (Street Rods, 55 chevys, pick ups etc). The camaro unit tips the shifter to the drivers side maybe 15 degrees and the shifter is set back a bit (Bucket seats and a console). I had a customer awhile back that had one in a 27 T coupe or early model A (He has both cars, I forget which its in) and the shifter would bump his leg occasionally. You could always make a shifter handle from a piece of stainess and maybe put a boot over the necessary dogleg but it will be a bit wonky.
Brand new Muncies (new case, iron midplate, new tailhousing and new gears) should be in the 1800-2000 dollar bracket; a street rod T5 will be 12-1500.
A double overdrive 6speed is huge in that car, might as well put a saddle on it; and in such a light car, the 2nd OD is pointless
Camaro T5 has a 2.95 1st gear; you could run a 3.08 in the back and never need the OD. Since it has the OD, I'd run a 3.31/3.23 or 3.42, at most a 3.55 for a nice cruiser with plenty of 1st gear.
For a mild 4speed stick car; Id run an M20 with at least 3.42 rear. If you need a beefier trans; skip the rookie stuff; the worst thing GM made was the case, and the pickings are pretty slim with the junk we see today. Get a new case, an IRON midplate and an aftermarket M22 or M22 wide ratio gearset. The cheaper gearsets are made offshore; the more expensive gearsets are made in Italy by Masiero or Euroricambi. If you want to go for the aftermarket gearset, I can send you some names.
If you are building or buying an upgraded Muncie and you don't have a clutch yet; the important thing is usually to keep the same output spline count, BUT I would ask your builder to use a 26 spline input regardless of your output.
If it was me; I would go with a 27 spline output (turbo 350 yoke) because it has more mounting holes on the tailhousing for the shifter 'box' than the 32 spline (turbo 400) tailhousing (which only has 3 holes drilled and tapped)
This means you have more flexibility in getting a comfortable shifter position. I would say this is more important than either the strength of the 32spline output OR even having to rebuild the driveshaft.
An aftermarket Muncie case (Called the 'Supercase' which is cast in America and machined here in house); is approx .150" longer than a factory case; this means your mounting foot on the rear of the trans will be pushed back the same amount, and the slip yoke will have to absorb the same amount as well. This isn't usually a problem as you can usually elongate the mounting holes on the top of your crossmember to solve fitment issues (a stock driveshaft in a musclecar or 3 speed automatic swap usually has no problem if you keep the outputs the same).
For your application, I would get the trans mocked up in the car and plan on having to adjust the crossmember and driveshaft. I can send you a measured drawing of a Supercase - based 'Muncie' (either 27 or 32 spline, they're on the same drawing).
Regarding shifters; older Hurst shifters are better than the new ones. I would rebuild the linkage with the 'Pit Pack' that has the steel parts and not the nylon. Incidentally, I have NO idea what fitment is like with the shifter linkage and your car. I DO know that if you have to bend those rods, bend them COLD and that the 'tabs' on the end of your linkage are VERY hard steel, if you have issues fitting the linkage over the dogleg levers in the sidecover/tailhousing; its best to change the lever not hack up the tab. We make a tabbed washer to fit the smaller 'stud-type' levers in the later, larger 'bolt-on' holes. And contrary to Hurst literature; the 32 spline Turbo 400 sized output is NOT M22 specific; its YEAR specific. You could get an M20 with a 32 spline output. 1970-74 are 32 spline; pre 1970 are 27 spline outputs.
Whew Im tired