Here's what I've run into so far with fitting the Vans FFWD kit to my TMX-360 with forward facing/horizontal induction and Precision Airmotive fuel injection:
1. One of the fittings to the oil cooler (can't remember if it's input or output) is blocked by the oil filter adapter. You just need to order a 45 degree fitting instead of using the straight fitting that comes in the FFWD kit. You have to remove the filter to install it, but you'll need to remove the filter anyway when you install the engine. No big deal.
2. The oil filter adapter also blocks the standard Vans crankcase breather set up. I haven't sorted it out yet, but it looks like you just have to change the routing a bit. Also, not a big deal.
3. The mixture and throttle cables and brackets look like they're going to work fine with one minor exception. The bracket that is attached to the bottom of the sump locates the throttle cable very close to one of the exhaust pipes. I've seen a few builders fabricate a new bracket out of Al angle. I'm going to try tweaking the bracket. Not a big deal.
4. Van's provides a straight fitting for the inlet to the engine-mounted fuel pump, but that would cause the hose to hit the bottom of the prop governor mounting base. Mattituck supplied an extra 90 degree elbow with my engine, so I used that. That makes the hose from the firewall to the pump a little long, so I might have to shorten it. I think this problem might actually occur on real Lycomings as well, because I think I remember seeing the same issue on Walter's site.
That's about it. I haven't installed everything, but the engine mount, cowl, exhaust, and baffles seem to fit similarly to a Lycoming. There are so many things that you need to tweak in the FFWD kit (especially the baffles) regardless of engine choice that these are really minor issues. Also using the Precision Airmotive fuel injection rather than Airflow Performance helps quite a bit. I believe the AFP requires changes to the throttle and mixture cables and the induction plenum.
Dave