Unfortunately, given that the 390 is an FE series motor, the pilot length of the input shaft will be too short (7/8th long instead of 1 and a bit)
Are you sure its 28 spline input and not 10 spline input/28 spline output?
However if you get a large spline input shaft with a small block pilot shaft langth ($120usd ish from memory from www.KajunJon.com
they're in Whitney, Texas, great to deal with) you can run the box behind a Clevo. However you'll need a suitable clutch setup, a Big block throwout bearing and either a modified small block clutch fork or a big block fork.
I'm currently running a Large input toploader behind my Clevo.