I'm installing a T-5 Mustang transmission in my '74 145 using V-Performance.com's (John Parker's) adapter plate.

I thought I should write out some notes, and here's as good a place as any...
Mine isn't in the road yet, so some of these things may not work out like I hope, but I've been pretty careful, if a little inventive.

T5 specifications and information are available at several Mustang web sites.
Try www.fordmuscle.com.

I got a T-5 from a '87 T-Bird turbo coupe, which has slightly closer ratios than a 5.0L Mustang. Additional differences are a slightly longer (.25") input shaft and more significantly, a longer Front Bearing Retainer tube. These were usually made OEM of aluminum. The throwout bearing slides along this shaft.
On this model, the tube had to be shortened about 1/2 inch to clear the clutch plate when it was all bolted together. I actually used a large tubing cutter to shorter it, saving a minor disassembly, or avoiding hacksaw tailings. Steel bearing retainers are a common retrofit and widely available.

Other parts you need:

Output sliding flange/yoke from T5 Mustang.
Pilot bearing to match the tranny. 5.0 input shafts fits volvo pilots. 2.3L shafts require Mustang 2.3L bearing, which fits in Volvo crank.
8.5" clutch plate from a 2.3L Mustang. Got at Napa.
Mustang throwout bearing. Larger I.D.
Shifter and handle to fit T5 (OEM or aftermarket)
7/16 hex bolts.
1/8" square tubing - 2 inches long
3/8 (brass) plumbing nipple

Getting the throwout bearing to fit well took a little grinding off the ends of the Volvo clutch fork pins. The pins on the Volvo clutch fork are about 1/2" diameter cylinders. The Mustang bearing has about 3/4" space at the waist, leaving 1/4" to make up to avoid rattling. The clutch for pins must be shortened just slightly (2-3 mm) to allow the bearing waist to fit between them.

My solution was to procure some small squarish brass plumbing fittings that , drill them through to fit the Volvo clutch fork pins, and shorten them to length. When the bearing is inserted between them, there is negligible play. I hope the brass will help avoid binding. There seems to be enough material all around the pin to be strong enough for this load. If they fail, they are small enough, I hope, not to interfere. I wanted to make bronze guides, but couldn't find material nearby.

The adapter plate consists of 2 parts, and is very nicely machined BTW. A stepped ring is supplied to fit the bellhousing and align the adapter plate precisely with the bellhousing, instead of relying solely on the bolt holes.

I would recommend a preliminary assembly WITHOUT the pressure plate to allow visual inspection of the pilot bearing and clearances to the bearing retainer.

Replace the clutch fork boot before mouting the adapter plate. (BTW I made a custom one out of leather, couldn't wait for shipment.) Mount adapter to bellhousing first, then slide in tranny.

Of course this is all more easily done on the bench. I wanted to paint the engine bay, so it worked out for me. It's not a one day swap, unless you're really determined and can get a driveshaft built overnight.

The speedometer hookup I'm just taking a guess at... The T-5 came with a combination electronic/mechanical pickup, with the mechanical part plugged off.
With the pickup removed tranny fluid will pour from the hole, but when it's in place with the plug taken out, it doesn't, so I'm assuming it won't leak. It'll drive my volvo speedometer, although the ratio may be different. We'll see, said the blind man...

To connect the two, I made a ~2" extension of the cable, using small brass square tube (available at better hobby supply stores), brazed to a short sectio of square steel stock ~3/32". I hope it holds. A 3/8 brass NPT nipple screwed into the plastic housing of the speedo pickup seems to allow the cable nut to be secured. I will cover the whole assembly with a section of hose with clamps or ties.

I dropped the assembled engine and tranny in place last night, and lo, the shifter appears exactly in the middle of the shifter hole.

So what remains are the rear tranny mount, which I can see will take an intermediate piece, and then measuring for the driveshaft and convincing the shop to mate this gigantic Mustang spider to my dainty Volvo spider.

I hope this works okay, because I've pretty much used up my allotment of Volvo wrenching hours this year. The 8-bolt b20 I removed is a perfect candidate for a performance rebuild, though.

And then I was wondering how pretentious it might be to put a T5 emblem on the tailgate...