If I were you I would opt for a TH200-4R instead of the TH350. The cost will be about the same and it will bolt right in (if you get a BOP version). All you will have to do is drill some new mounting holes in the frame for the crossmember, install a TV Cable kit, and a shifter conversion kit. The stock driveshaft length is the same as the Jetaway as are the input and output shaft splines. Not only do you get a 0.67 overdrive gear for the highway (which reduces the engine RPMs and gets you better gas mileage), but you also get a 2.74 1st gear for better off the line acceleration than the TH350.You Oldsmobile fans will recall the Jetaway 2 speed with the switch pitch stall converter, aka the Junk-away.
I will swap it out for a good Turbo 350; I understand it fits right in.