My biases. My preferences are shaped from my own flying, decades of reading a lot of aviation press, and 20+ years of chatting to other EAA members. My rank ordered preferences are Lycoming, Continental, Rotax. I rank the auto conversions alongside the the exotics commonly seen pre-1950: Hirth, Gombe, Ken-Royce, et al. If I were building something with low wing loading I would have high confidence in my ability to find a survivable landing site. But the Cozy is built for travel between hard surfaced runways over 3500'; it makes sense to stick to the reliable makes, which I see as Lycoming & Continental.

Buly Alieve is a respected Cozy builder. Following are his biases plus some of my own.
1. Dual electronic ignition from the start.
2. Updraft cooling
3. Dynon sensor harness from Stein Air
4. baffling kit from Vans Aircraft
5. red Silicone valve cover gaskets
6. push-pull marine control cable for throttle with vernier fine tuning
7. 90 degree oil filter adapter
8. Kavlico 3 wire OP and FP sensors
9. B&C Starter
10. 2 wire Oil Temp sensor
11. Steve's gas collator

Engine on hand. As noted in "research", the selection of a Cozy IV was partly around its ability to fly well with an IO-360. I have an IO-360-A3B6D, originally from a Mooney, then used in a BD-4 until removed for overhaul. The engine was never reassembled, so I have a full set parts ready to assemble with aging yellow tags. When I last flew this engine, it had the dual mag on one side firing one set of spark plugs, and a Klaus Savier Lightspeed ignition (generation 1!) firing the other set. This gave 90+% of the benefits of spark advance with the simplicity of a traditional magneto. I never liked the dual mags on one shaft, and that stops with the dual EI. From the engine pics you can see that the A3B6D has a prop-facing air intake. Since I'm going to a pusher configuration I'll see if I can rotate or swap the oil sump - I'm pessimistic but its worth asking the question. And this is a wide angle / angle valve engine. While that's a better geometry for the valves, the stock engine for the Cozy is narrow deck / straight valve. I get to do a custom cowl, and probably a custom exhaust.

There has been some progress in the 30+ years since the Lightspeed ignition. For a few of the manufacturers I am comfortable going with dual electronic ignition. SDS has the most installed systems, has been the manufacturer behind other EI brands, and has a good reputation on the Cozy builders forum. As a result, I plan to build the engine with SDS EI and FI, and hope to sell off the mechanical FI and the dual magneto originally used on this engine.

Attached are photos showing some of the SDS components and installs in other aircraft.