You asked a vague question to which any response would be highly subjective. There's a wealth of information on this site but YOU need to invest some time to find it, read it, and digest it.
Do you want a turnkey car? Look at Superformance or CAV.
Do you want a monocoque? Look at RCR or at Goram's offering (he's in Sweden and can produce amazingly accurate monocoque chassis). Look at Superformance or CAV.
Do you want a space-frame kit? Look at the UK offerings - Tornado, Southern GT, MDA or again at Goram's monocoque. Look at the Aussie offerings - DRB and Roaring Forties, who appear to be bringing an excellent product back under new ownership.
Do you want something low budget? Well, truthfully, you shouldn't be looking at a GT40 if you have a low budget. Scour the classifieds for someone who needs to get out of a partially built kit. Look again at Goram's space-frame offering, which I believe to offer tremendous value.
Bear in mind that all these manufacturers are small businesses and that any one of them could make like Roaring Forties go out of business between the time they accept your deposit and the time they are supposed to deliver your car. Only one of these manufacturers, RCR, is based in the US. Do you feel comfortable sending a deposit to an overseas manufacturer? Ask how many examples of each manufacturer's car have been completed and on the road (only half of the manufacturers I've mentioned actually have a track record of customer-completed cars), and evaluate their market staying power and their after-the-sale support, or lack thereof.
Don't ask us to tell you what to buy, do your homework, ask informed questions, and decide for yourself.
