So I do have 2 other options,
Advance Adapters makes a 15mm thick $475 adapter to bolt a W56 bell to an 86-95 R150/R151 trans, eith a custom extended pilot bushing that hangs out of the crankshaft a ways since the adapter makes the input shaft no longer long enough.
I'm not certain exactly where the input shaft will be with a 3/8 inch thick engine to bellhousing adapter and the VW engine in place of the Toyota, but this might give me pretty close in length to using the longer input shaft.
Also I can use a much more expensive 18.5 degree maximum clockable adapter from TD Conversions/Northwest FabWorks for the 1996+ 3.4L 5VZ V6 bell, but it is 2" thick vs 3/8" thick, costs more, and uses an aluminum crank hub adapter that doesn't take the stock flywheel bolt torque specs. In a Samurai, an extra 1-5/8" or 2-5/8" drivetrain length is pushing it, although I do fully plan to stretch the Samurai frame to SJ413W LWB body length or SJ413K pickup bed (same frame length & wheelbase, 93" vs 79.9").
The longer input shaft for 1996+ transmissions is still available as it is used at least up to 2018 or 2019 Land Cruisers. The 86-95 short input shaft is a used-only item, NLA from Toyota.
My other option would be to machine a 1-inch spacer (give or take some thickness) to push the bell housing off of the adapter slightly, and use extended dowels, or also I could use this 1HZ Toyota diesel engine bellhousing and mill down the transmission side into a spacer about 17 mm thick... That will change the geometry of the clutch fork slightly if I put it on the transmission end, however. But the Advance Adapters kit does the same.
Obviously the easiest would be to go with the V6 bellhousing and the TD Conversions clockable two piece adapter kit and crank hub adapter, but the Doomsday 20-degree clocked 22R adapter is pretty ideal. Their 3VZ R150 to VW TDI adapter is only clocked 15 degrees, and I don't want to have to clock the transmission and transfer case 5° or even 3.5 degrees due to a very narrow transmission tunnel in a Samurai which will already need widened, I can't move the seats outboard any further!