Dan,
I am just completing a Revmaster R-2300 powered Onex.
There are a few firewall forward differences to consider.
Firstly, the crankshaft is about 2 inches longer so the cowl will need to be extended.
I added 2 inches of glass to the rear of the cowls which worked out fine.
The scoop for the carburetor was done by making cardboard templates from which a foam block was shaped to suit. Fiberglass was added to this and then the foam removed before being attached to the lower cowl.
You will also need to add a slot for the lower oil cooler.
Also beware the markings on the cowls for cutting the head openings are in the wrong place for a Revmaster.
The baffles are very different to those on the Aero Vee so I would not waste the money on buying them.
There are drawings of the Onex/ Revmaster baffles online but if you cannot find them contact me directly.
snelson330@gmail.com