Yup, that's true, but I've just recently found out that there are a few other little differences that have to be addressed that almost make the Mustang unit a better starting point.
In fact, I got one of those 4.2 truck 4R's for my swap.
THEN I found out that they're longer than the Mustang AOD/E or 4R, much like some of the AOD's from light trucks and Lincolns were longer than Mustang AODs. I've got an 89 Linc Mk7 with a "long" AOD, so thought I'd be all set with a 4R, then found out the truck 4R is also longer than the Mustang 4R - so now I still have to mod my trans mount and shorten my driveshaft, something I wouldn't have had to do with a Mustang 4R. Now swapping any 4R into a Mustang for an AOD you still have to deal with a ~1" longer trans as the "regular" 4R is about 1" longer than a "regular" AOD.
Another small but annoying thing is that the manual lever points DOWN on the truck unit, not UP like on a car, so the manual lever shaft had to be changed. Not THAT big a deal when going thru the trans, but still - -.
Whether starting with a Mustang or light truck unit, you likely will want to go thru it anyway and adding that extra direct set is simple with the existing direct drum, so everything considered the Mustang unit would be easier to start with.
Otherwise, yes you need a Baumann control if you go 4R or AOD/E unlike if you use the AOD case and swap in 4R parts. And the Baumann control
does take care of the speedo thing.
If budget is a critical factor, and it can be after you buy the trans, the overhaul parts, and hire it done plus the vb mods if you can't do them yourself, plus the Baumann control, it can add up. So if that's the case, you may want to consider a converter from
www.roadrunnerconverters.com. They rebuild police Windsor bolt pattern AOD/E converters with heavy duty lockup, they braze the fins, up the stall some, and do other internal improvements to up the anti-ballooning limit and sell it for ~$200. With my fairly torquey 351 I should see 2500 to 2700 stall. Granted it's not an Edge or whatever, but if $300 makes a difference it's an option, and they do have a good reputation.
I've researched shifters and found that ones out of Mark VIII's and TBirds with 4R's are VERY close to my Mark VII and should bolt right in, and likely would be easy to install in a Mustang that came with an AOD (I guess Mustang with manuals have a different shaped tunnel which has to be modified to fit an auto - see
www.lasotaracing.com).
And you DEFINITELY want a 98-up 4R whether you put the parts into an AOD or use the whole thing. That's when they started using the mechanical diode in place of the one way roller intermediate setup which is a potential weak point with major destruction if it fails.
And the innards are the same (with the exception of that one direct clutch set) between mod motor V8 units and the V6 units. Now the 5.4 trans has an even stronger gearset and a couple other small durability upgrades, but a decently prepared 4.2 unit will easily hold upwards of 500 hp depending on who you talk to.
One thing about swapping the parts into an AOD, the AOD output shaft has to have governor feed holes which the 4R's don't have, and the only stronger available shaft that'll work is out of the 93 Mark VIII which had the 1st version of the 4R but still had the governor holes. You might be able to get your AOD shaft hardened for some improvement, not sure on that.
Here's some newly discovered (for me) AOD tips
http://www.clickclickracing.com/tech.htm
http://www.clickclickracing.com/forums/showthread.php?t=2444
Also be sure to check out the links in that LOL article, especially the
www.tccoa.com tech/trans articles.
