So I've been doing some digging
I'm a sucker for a challenge and none of the off the shelf rotrex kits are going to fit this car, as they all fit on the exhaust side where I have no space. The immediate problems I've faced while designing this in my head are the availability of 4 rib belts, and to run it with a single serpentine belt I will need a double backed belt so I can run the rotrex off the back of the belt, otherwise it'll be spinning backwards with the engine.
There are not many 4 rib double sided belts on the market at all, furthermore I think a 4 rib belt is pretty poor for a supercharger. This got me thinking, is a 6 rib pulley available???
The answer is/was no... however.. while searching I stumbled across a Honda D series forum, where a few people have built D16 strokers with a D17 crank. What they found was that the D17 crank snout was much bigger so they either had to use the D17 pulley/oil pump, or turn down the snout to use the original bits. Then some further searching on this topic revealed that some people had used B16/B18 crank pulleys on the D17 crank.... therefore a bit of reverse engineering tells me a D17 pulley should fit a B18C crank... and... it's a 6 rib pulley. Bingo!
I've also found out that the alternator pulley is the same ID too... so I can convert to 6 rib for peanuts and already have the bits on the way to check offsets etc. but Any minor difference in offset should be easy to put right, if needed.
Now as a lot of OEM serpentine belt setups utilise a 6 rib double sided belt, this means there's a myriad of belt lengths available off the shelf.
I'm just going to keep collecting bits but as far as I'm concerned the hard bit of designing it out is already done now and I can run a better belt than the other kits and run the rotrex above the alternator where I have some space.
Little sketch, obviously a tensioner needs to go somewhere too, maybe near the alternator