i have a mag (autoexpress or autocar or something) that tested the 0-60 of the mk.1 172 against proton gti, 206 gti and they managed 6.6 secs. Ive kept that one in good condition...
Id say theyd be as quick as a willy (although i havent raced one yet!) considering the factors. Willy weighs something like 980 kg or probably less for the willy 1s, 172 mk.1 weighs 1035 or thereabouts, so willys going to have simliar power/torque to weight etc.
the performance really depends on the driver. Different frogs, different times. You have to be in the right frame of mind to get the best of of the car, i guess the same is with any car really. Have fast you shift, and when you shift etc. Whether A/Cs on or not. Some days it performs like a BOAT but others its like a completely different car and really really flies - quite strange really. Quite impressed with it considering the death its been given. 36,000 miles of red lining/limiter and clutch dumps and its only had 4 gearboxes haha. Seriously tho, the engine hasnt blown up yet which is pretty impressive i must say.
If you bought one second hand now, the owner may have purchased another warranty available for another year or two which is proper helpful i tell thee. AKA could save you a fortune......
problems with mine: obviously gearboxes, idle control switch replaced, mid silencer i think has been replaced cant remember, new clutch due to old one juddering like a nympho sat on a washing machine (probably my fault), windscreen replaced about 3 times i think (my fault again), windscreen trim blew off racing a CTR at airstrip speeds (probably autoglasses/my fault), clunking under acceleration - gearbox mount fixed underwarranty. Nothing really that bad to be honest apart from the gearbox, considering the thrashing.