Marc,
Current plan is to build the mount ears into the housing (At least the uppers)..............Still working on the lower mount ears (May be bolt on to the housing with reinforcement forward under oil sump)............The Mazda front housing (Aircraft Specific alloy version) will be machined entirely from billet 7075 T6..............
The Aircraft specific alloy housing can be drilled for any of the slight bolt pattern differences of the stock Mazda front covers...........The gasket pattern are all the same except for bolt spacing and an extra bolt or two on some housings............The only replaceable part you might need would be the water pump cartridge...........I currently have both 2004-2008 and 2009-2011 RX- 8 Renesis front covers............The 2009-2011 cover has a rubber "O" ring gasket on the water pump and has a oil filter pad built in...........I like the "O" ring water pump but consider the small stock oil-filter to be too restrictive for the 100 psi oil system of an aircraft engine so would use an external oil filter...........A substantial amount of the Renesis cover is not needed and can be machined away if wanted.........
Early 13B / 20B front covers will fit but the alloy water pump housing will not and the cast iron pump cartridge is heavy plus the early ignition may not clear mount tubes...........Will look further on the ignition to verify clearance problems.............
As you said there are two versions of the Lycoming mount ears...........The ears are "No. 1 Dyna for 30 degree Ears with 1.385 inch cushion holes" and "No. 2 Dyna for 18 degree Ears with 2.00 inch cushion holes"...........Vans RV10 mounts use the "No. 1 Dyna 30 degree mount ears and they are the ones we intend to use on the proposed alloy housing.............What mount ears are called out for the "SeaWind" engine mount ?.............I am presuming that the IO-550 uses the same ears as the IO-540.............When I purchased
RV10 mount rings from "Van" their website indicated that they could make their RV10 mounts for the "No. 2 Dyna 18 degree 2.00 inch ears on special order (do not know at what price---I purchased two "30" degree Mount Rings only for $150.00 each...........
Just for your information I have a set of four new Lycoming # 72306 18 degree "Dyna 2 18 degree mount ears for the 2.00 inch mount cushions that I bought before I know as much as now...........Still In box I received them in.............Will sell for what I gave for them $450.00 and pay shipping.............See attachment.......
Best
Kelly Troyer