I won the D1GP BRZ's engine the other day, and promptly put it into the Silvia Q's (S13) that I had, complete with the lime green two-tone. Haven't tried it yet, but I don't think I actually will drive it until there are regulations that permit it. Just like most cars I have in general, with or without an actual engine swap. Though I did recently use my 2JZ-swapped GR Yaris for the WTC 600 event at Grand Valley.
I also still have that Escudo engine, but I think instead of waiting for it to potentially become compatible with one (or both) of the Swift models, I'll just put it into the Lancer Evolution. Why? Because it's 4WD, so it'll likely have better control with all that power. Especially if I can install a torque balance controller and set it to 50:50.
But that still leaves me with a spare LS9 from the Corvette C6 ZR1. I suppose it could make sense if it ended up being compatible with the GTO Judge, but I could also see it becoming compatible with a couple JDM classics that don't have something yet, like the FC RX-7.
Then there was that Aventador SV engine I had to spare, too. I really, really hope it ends up being compatible with the Miura Prototype. Maybe more realistically, it could go into the older Countach LP400, given that it already can go into the 25th Anniversary version of it.