>>28562551
Anything that is light, winds up high, and has a peaky powerband is fun in a chassis like these. I've heard the same complaints about the Duratec, but even still, it'll be quicker and way more fun to drive than anything else for the price. I have a buddy who regularly tracks one with a Duratec and, afaik he hasn't had any major issues. I haven't driven his, so I can't remark on how it feels to drive in comparison to other engine optipns. I've driven a K20 Locost and can confirm it was pretty excellent. They are great engines for this type of car.
My Locost has a GSXR-1000 driveline in it, which I definitely would not suggest if reliability and street driveability is your goal. It's way more fun to rip than a car driveline with the sequential and 13k rpm redline, but has its fair share of quirks to deal with and is a pain to drive on the street (and obviously won't be an option through caterham).
What other engine options are available at your dealer?