Well, I have a set of chassis drawings should you need them. Definitely check the bracket at the base of the rear axle casing and see if the bushings are in good shape. Dear old dad had the bracket part ways with the axle on his early Cateringvan, luckily at low speed. The axle actually pulled the driveshaft out of the gearbox and left a large bulge on the tunnel. I hate to thing what would've happened at speed. Also have a look at the upper trailing arm mounts at the chassis end.
The unfortunate thing about the Lotus built S2/3 chassis is it does lack the triangulation that the S1 had, and what Caterham added, so there could be some chassis issues if the previous owners have "improved" it. The steering rack mounts aren't the best but can be easily modified to make them stronger (Caterham did this). The lower chassis tubes are hidden in the cockpit area, so no easy way of inspecting them without removing the ally cladding.
Other than that, they are very simple to work on, very fun to drive, and if it's a crossflow then relatively easy to make decent power. The single downdraft, though stock, makes next to no power. I was very unimpressed with the one that came through the shop in stock form.
Good luck with the search and please post pics if you do get one.
