if you rebuilt it before breaking it, or it's in good condition to begin with, it will handle a fair amount of power.  the V6 commo input shaft bearing is supposed to be an upgrade, but i don't know how it's fitted (is it full box teardown etc?)

I measured up the input shaft its the 6 cylinder one 167mm, the V8 one would of been 20mm longer if I remember correctly.   Doesnt really matter at the end of the day...a T5 is a T5, it'll break once I put some power through it....wish I could be as certain on winning lotto.

crossflow T5 bell and EA to EL will accept any 6cyl T5 box   V8 one has a longer input shaft, so probably could fit with a spacer(if there's enough room for the throwout bearing still, but then it means the tailshaft needs to be shorter if so, i doubt anyone would do that mod unless in a custom car)

picture of the bellhousing area m8,but looks to me just like a normal t5, pre world class are early t5s,easy way to tell 1st gear ratio put it in 1st and turn the shaft by hand ,mark it b4 doing it and 3  1/4 turns is 3.25.1,well thats how i did it with a xg box i put in ryans xe with a 351c and custom bell to suit 6cyl box.

According to goggles that number correspondes with a Non World Class mustang T5....confusing   Pretty sure its to box that'll only take 300lb's of torque...better be gentle with it🤣

Pretty sure the first gear is 3.25, the ute was effortless in smoking the rears in 1st or 2nd and first ran out wayyyy to quick.   I could be wrong but I think the XG longreach had a 3.25 as the first gear...I'd have to find the service manual to check.

I'd have to climb back under the car to take a pic, but i've measured the input shaft and its only 167mm so pretty sure the box is a six cylinder one, maybe the extension housing is from a v8, thats what i took the number from. Its marked 0552-0662903.  Once I clean the rest of the box I'll see what numbers are on the the main housing.   I do know the box has a lot less kays than the rest of the car.   It'll do until my funds start to recover and I can get a TKX in to it😁

yes yes yhes there is an adaptor made in usa for ford 200 250 mustang to suit the t5z sold by variuos companys like holley and scott drake,also suits slant 6 so check does yours have the adaptor to space it out.