"A sealed Vampire pedigree." My personal favorite among Japan's fighter plane projects is Mitsubishi J4M1 Senden. Though it was developed starting in 1942 as an interceptor fighter, its intended target at that time was heavy bombers like the B-17, which was not as fearsome as the B-29. And so I believe it was not a specialized high-speed model like the Shinden but rather a general high-power airframe in all categories but cruising range. Though I suppose that in the light of day it is just another victim of Japan's chronic runaway engine woes. In fact, though there is no way this could have been a consideration at the time, it should have been possible to outfit the plane with a jet engine. Well, at least wouldn't it be more realistic than adding one to the Shinden, where you wouldn't even know where to put the jet intake? Shinden fanboys hold in ridiculously high regard the J7W2 Shinden Kai, a jet-powered Shinden concept, but it makes me want to say, "Stop making excuses for that plane by adding tiny intakes and realize that a jet engine just won't work, LOL." But take a look at the Vampire Trainer at the Japanese Air Self-Defense Force Hamamatsu Air Park, and it's easy to imagine the Senden Kai!
The Swedish twin-boom aircraft the Saab 21 saw its piston engine replaced with a jet engine and became the Saab 21R, a jet plane like the De Havilland Vampire.
