In my opinion
K series will be best bang for buck, modern technology. very easy to find parts as alot of cars from 2001 to 2011 (in the uk) share alot of basic parts like cam and crank sensors, coil pack and the list goes on
In this day in age, you can kswap cheap from around £3k to £5k depending if you do your research and get good deals here and there. i have made a post on the kswap part of this forum showing what parts you can get to cheap on and what parts to avoid like the innovative engine mounts and so on
Now you can spend more on a kpro/haltech ecu, get branded parts and so on and the price will increase.
I have tried and tested both branded parts(My own build)(I spent £10k back in 2016 going kswap) vs my friends build(all ali express parts and cheap parts here and there)(spent £3.5k including kpro ecu) and there is so many thing you can get away with cheaply, only things i wouldnt cheap out on would be injectors(if ur setup needs to replace it), fuel pressure regulator, any engine sensors.
Theres literally max 5 wires to splice from the conversion harness to the stock ek chassis/ecu loom
My genuine innovative mounts snapped after 2 years of driving and withen 1 year i had to replace all the bushes. no track days, just driving here and there.
mY current ali express hasport copy mounts have lasted 7 years with no issue to the bush or anything.
Now if you want to keep it period correct. b18cr would be perfect with the correct final drive gearbox. make it fun and nice to drive. I have seen just engine and gearbox go for around £4.5k.
I have a few friends who have b series and all of them have dizzy issues, now unless you go coil on plug, that would be the best solutuion to avoid the dizzy issues
H22 i wouldnt unless you really want to be diffferent, but the support there is very minimum
f20c, havnt seen anyone put one into an ek at all in my all years of being into honda
this may be all over the place as im typing this while at work, while serving customers, picking up phones, getting up etc
