We have a 1600cc unit here with Arden crossflow cyl head & 6 speed dog engagement gearbox, with full race cam & 13.8:1 compression ratio etc etc etc-->super dooper gnarly thing really, sounds like a V8 sprint car (well ok, maybe not quite like a V8 sprint car but close)
My road mini engine is a nice tame smooth drivable 1510cc donk & lasted about 8-9 years of thrashing around the road & club races nearly every 2nd weekend & then a Targa Tasmania rally & then even more club events after that & am rebuilding (just rings & bearings) it again at the moment,
1426cc is easy enough, (74.7mm -->or 160thou oversize) just that offset bore needed & most commonly need to plug & re-drill offset the end oil galleries, easy done no problems
Add stroker crank of whatever offest you like & away you go
& there are 2 common pistons avaliable for that type of engine, (amongst others that are not so common but still quite avaliable if you look around) first is the one Kev/Dr mini suggested & that`s the short triumph 2.5 piston, (they`re the ones i used) which dictates the use of a very small cc cyl head chamber &/or shaving the block (either way it`s no drama) but you can also use the triumph 2000 piston which is the same bore size but quite tall & will need to knotch out the number 3 piston if using them in conjunction with a stroker crank just to clear the dizzy drive gear,(i don`t like doing that tho) so maybe do what i do & skim/slim/trim/thin down the dizzy drive gear---> easy-peasy
