You can right click on Nick's user name to send him a personal message or e-mail (if he has enabled e-mails). But I don't know if you're going to have any luck getting in touch with him, since he's only posted a few times and only to this thread.
Sundstrand-drive machines don't have a backgear unit, so your low-speed performance with a VFD is going to be pretty poor. Even if you did have one on hand, there isn't space to install it unless you carve a huge hole in the bulkhead behind the motor to make room. I would hate to see the old girl butchered up like that.
I hope you'll reconsider the conversion. An old-school automatic transmission mechanic or hydraulic pump mechanic might be able to fix the existing drive for you.
a VFD with a 10HP motor and no backgear would have better low RPM performance than a Sundstrand drive in good condition. For that matter, a VFD with 5HP motor and no backgear would be better than a Sundstrand drive at low RPM. I seldom use 500 RPM on mine.
DMTWO, the Sundstrand drive should run in reverse. Maybe it is just a matter of linkage adjustment.