So I decided some time ago to modify my 2003 MTD Yard Machines by converting it from Vari-Drive to a 5 speed manual.
First, I grabbed a Foote/Dana/Spicer 5 speed from my local junk yard. Cleaned it out, and welded the spider gears solid. Changed the drive pulley to 4" and added 90w gear oil and RTV sealant.
Then, as I'm prone to do, I just jumped in and started stripping down the machine and prepping it for the install without really knowing what I was getting into. I ripped out the Vari pulley and all the mower deck hardware. Next, I mounted the tranny to the body just to see if everything lined up.
It didn't.
The drive pulley was 1.25" to high and would not line up with the engine pulley.

Solution: Put the tranny on blocks. I took tube steel and cut them to size, and then drilled holes through for the mounting bolts.
After all this, I put the blocks in place only to realize that the mounting bolts on the tranny didn't line up with the body! The tranny was too wide. LOL
Ok, so I'm batting 1000%
Solution: Make adapter plates. I took some plate steel from the old bagger attachment I had and made two square adapter plates.
So, with the height and width adjustments made I was ready to start the process of creating a drive line.
First, I cut out a slot in the body in order to install a piece of angle iron. This angle iron was going to be used to mount the clutch, and adjustable idler pulley.
Then, I built the clutch. I bent up a rod to connect it to the foot pedal. Installed the tensioner pulley. Then I drilled 7 holes in the angle iron for the adjustable idler pulley. This would allow me to adjust the tension as the belt stretches.
Next, I welded a eye hook onto the clutch for the spring to grab on to. I attached the spring to a turnbuckle for tension adjustment.
After that, I reinstalled everything and it's been great!
Here's a video: