It is the aftermarket Tremec Magnum 6 speed transmission and in my case it is about 1" maybe less once I got the crossmember installed.
In 2020 things got more complicated with the T56 transmissions as there are 3 to pick from...
- T56 made by Borg Warner found in the 4th gen F body cars - Reportedly this transmission in some cases will clear except where teh shifter comes through, other cases it will require more clearance.
- Tremec Magnum 6 speed - Aftermarket Tremec transmission that has been available for 10+ years, used in this thread/conversation
- Tremec Magnum "F" 6 speed (Magnum with the 4th gen tail housing with shifter) - This will put the shifter in the same spot as the 4 th gen, but see my note below.
When I talked to Tremec, they make it clear to me that their transmission is not a "T56", not sure if that is a copyright thing or to try to eliminate confusion, or because their transmission is better than the originals, but there are some differences.
Some things to point out that are different: There are 3 shift positions on the Magnum sold by Tremec. The forward most plate, if you wanted to use this shifter position, requires you to buy a special shifter that fits that location as well as a block off plate for where the shifter is positioned normally. The further back shift positions are easy to change, just flip the shifter 180 degrees. Anyway extra details that do not matter, the first shift plate was also found on the original T56. The only thing is GM used a thin plate in that location, where-as Tremec used a very thick plate, almost 1/4" thick or more. In other words, what ever celarance there is left with a T56 from the 90's, it may not exist with the Magnum F version.
Al intensive purposes the Magnum F and the T56 from the 90's are the same, except for the following: tail-shaft has different spline count; transmission mount is recessed, I think its 3/4" (cross member kits come with a plate to adapt for this situation); does not have the skip shift feature; stronger built than they were in the 90's.
ref:
https://tremec-blog.com/introducing-the-tremec-magnum-f-6-speed-for-3rd-and-4th-gen-f-bodies/If you are doing an LS swap, I would say consider a Magnum F for your swap, as long as you mount the engine forward 1", which I believe you would need to so you don't have to modify the cross member for the accessories, you will actually be moving the shifter forward 1.5" giving you plenty of shifter hum clearance. If you sen photos of people who do the swap with a 90's T56, it puts the shifter right where the automatic level would go, which is perfect ergonomically. If I was using the mounts that put the engine at the same position, which more recently seems to be the trend, I would go with the Magnum 6 speed with this shifter hump.
If you are using a BOP engine like it sounds you will be, keep in mind that the bell housing will be 6" thick (rather than 5.5" for a factory BOP bell) and will move the transmission another 1/2" back (like in my case). That 1/2". I am afraid to say that a Magnum F will most likely require a lot of cutting of the floor, though it will be all from about where the shifter comes up and possibly 2 ears where the forward shift plate is. If your confident with a hammer you could add clearance where the forward shift plate with some strategic dents in the floor.
Easier way to say it, I would go with a
Magnum 6 speed for a BOP swap and any LS swap where your getting special accessory setup to clear your front sub frame, and I would consider the
Magnum "F" 6 speed if I was doing an LS swap and mounting it 1" forward.
