Yes I considered the hydramat. Not much concern with having an uninterrupted fuel supply since it has a one gallon surge tank. Yes it'd probably take longer to clog up, probably long enough I'd never have to touch it again, but they're expensive, like $200+. Talked to a couple off road racers who say they just don't use a pickup sock and run an external filter, so that's my current plan.
I understand all that with the subframes and bushings. Going to stick with the rubber grommets on those added bolts. IIRC the holes for them in the subframe are quite a bit bigger than the bolts so they're not doing much lateral location except maybe from friction. That part of the subframe they clamp isn't super rigid so I don't think it will cause a lot of stress. The subframe bushings are very stiff too. Overall just not worried about it.
Gotta do more research on my own but could use some advice on the EZ36 swap.
Radiator - Leaning towards an early EZ30 radiator (they're thicker than the EZ30"R" and EZ36 IIRC). Need to check height. Considering some other aftermarket radiators, including for non Subarus, looks like there are a few with ~2" thick cores but they basically all have just one inlet. Worked around that on the black Outback but not really ideal. Also thought about using something shorter so I can raise the radiator support but I don't think I'm willing to go that far right now.
Fans - Assuming I'll need to use pusher fans again, will probably just see if I can fit a pair of these, they're noisy but work well:
https://www.summitracing.com/parts/spu-ix-30102045/overview
ECU - Leaning towards Haltech especially since they say they have a base map for the EZ36. Will have to figure out the best solutions for AC and cruise control to work with that. Assuming the EZ36 being drive by wire normally just has cruise built in to the ECU and just have to wire the switches to it. Would be nice if the AC wasn't just hotwired and frosted up like my black Outback.
Exhaust - Assuming the engine won't come with full manifolds/headers I plan on buying Raptor headers, they're the only kind I've found much info on. They supposedly sell "Impreza swap" headers but I didn't see them on their site. Some heavy wall tube to the back and then probably a stock EZ36 muffler if I can fit it. Open to suggestion here but want it as quiet as possible.
Might use stock airbox/filter or might put a GM Vortec centrifugal style filter like I have in the black Outback, seems to work well.
Need an earlier EZ36 so the power steering pump bolts on right?
Assuming I can make the AC, fuel, and coolant lines work. Returnless fuel pump for the EZ36?
Aside from that, need to get an STI driveshaft and R180 and put a low range in my other 6MT. Very tempted to maintain the front CV height at the trans but tip the back end of the trans down to get the front of the engine up for better approach angle. Will hopefully start on the billet rear knuckles this week. Need to fab a bumper and skids too.