[JLMounce]

Originally Posted by Half-Inch Stud

Since you have a 455; Find a posi for your existing rear. And Swap to TH400. Done.

The idea of a Street 455 with anything over a 3.31:1, even a 3.23:1 is fraught with yuk on the highway. If ya must, then the 4L80 with the vacuum modulator kit allows manual-shift with switches on the shifter, no computer.

HEI in place of a points dizzy.

I had 3.73's behind a standard street build 455 and moved down to a 3.31. I never missed the 3.73's and I honestly thing the car picked up with the 3.31's anyway.

From doing my 4l80e, the things you don't really hear or read about is the need for a counterbore slip yoke in the driveshaft when using 2wd variant with a bolt on tailhousing. However for cars where a factory speedometer is preferred, opt for the aftermarket mechanical drive tailshaft.

I run a dakota digital speedometer drive which works well, but it ads complexity and another electrical component.

Installing the 4l80 in the trans tunnel of a '72 should work, but there may be some coaxing with a BFH. If you have the ability, try and find a 93-96 core that has the feed and return cooling lines just behind the bell housing. It will aid in installation. You'll also want to use aftermarket cooling lines with 90* banjo fittings.

For the trans cross-over, I'd really try and use the factory unit and either move it or modify it to work. The aftermarket stuff is really big and really rigid, which transfers unnecessary NVH. Use a stock type rubber transmission mount. Stay away from the poly stuff. It's too hard and with rubber engine mounts can cause unwanted NVH as well.

While the vacuum modulator certainly works, I'd still recommend a proper computer. I run the US Shift Quick 4 and it's been great. The support from Baumann Electric is also top notch.

Based on the OP's planned build, I would run a near stock rebuild with a shift kit. Mostly just to do the pump mods and dual feed the direct drum. No need to do much with the pressures. I'd use a rebuilt factory converter.

I will say though, with the computer control and the TSP triple Kevlar disc converter is a pretty cool combination. I use the torque multiplication of the converter in 1st gear to get the car moving, then lockup the clutches in 2nd gear at 4000 rpm. It's pretty crazy to grab rubber on the 1-2 shift, then grab rubber again in 2nd as the TCC locks up.

It's a ton of work to accomplish, and not the least expensive thing I've done, but the performance and drivability gain is huge.