That thing is frighteningly perfect for this kind of thing. Looking at your pics, I would actually belt drive that thing - it would make the unit more compact, and you won't need to modify it at all. The biggest advantage is that you could "fine tune" the drive ratio to optimize motor power vs rpm based on your application. In other words, let's say your motor has a peak RPM of 50,000, and it's "sweet spot" for maximum torque is 40,000 rpm, but you only need 30,000 rpm impeller speed to achieve your hp goals. If the cog pulley on there is 24mm in diameter (for example), then you'd need an 18mm motor pulley and a short belt. There's really only 3 pieces you need to make and the entire motor/blower assembly only costs around $1,000 - less than I have in my current setup, and mine is bulkier and took a lot more work.
Forgive my (non-existent) TinkerCad skills, but this is the most complicated piece - and it's pretty simple - to make. The motor plate:
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The three holes in an "arc" are supposed to be a smooth, arced slot - I just don't know how to do that in TinkerCad. The motor gets bolted to this plate, the "ear" with the single hole is your tensioning pivot bolt; the arced slot is your belt tensioning hole and then just two fairly thick walled spacers to space the motor plate off the back of the blower - like where you're holding the motor in this pic of yours:
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Of course, the exact location of the "ears" on the motor plate should line up with the existing holes on the blower - they'd probably end up not in line with each other. All we need is to find the pitch of the gilmer pulley, locate pulleys that'll work (one of the members on here is a machinist - WB Projects - he's got a CNC setup and could actually make them, I'm sure.) Heck, you could make one on a manual mill with an indexing head if we can't find any. And of course, see what belts are available. I'm not worried about the belt being only 1" wide.
The primary reason why powerdynes would break the belts (back in the day a lot of Mustang guys ran them; since my car is basically a Fox chassis Mustang with a 5" longer wheelbase, I've been a member of a Mustang forum for over 20 years - I remember those issues) is the sudden shock loads from gear changes (mostly stick shift guys) would destroy the belts. We don't have that issue.
This makes things SO easy. Can you see if you can figure out the pitch of the pulley so we can start looking around for other pulleys and belts? I'm fairly sure I'll be ordering one of those blowers in the very near future because I've already got a second motor, and my new LTO packs should have plenty of power to run two e-turbos. Thanks to you, I think my next phase will now be running twins. Well, not twins exactly, but close enough - my current Si trim and this thing - which is basically a copy of mine with a much better suited drive/back plate.
Thanks again!