Before you use an SPI, the early engines had smaller ports, and different cams to the later engines produced alongside the MPI, so its that late head you want. First points to note:- Yes you can skim the head, about 20 thou will bring you up from nominal to top limit compression (just over 10:1) and gives a useful boost to mid range torque. Can you use a 1.8 cam, no, the 1.8 uses the same cam as the 1.4 MPI (2.0 is either a V6 K, or a different engine altogether), however the VVC uses a higher lift/slightly longer duration exhaust cam, this can be used straight in your exhaust, it can me modified to take a rotor arm to use in the inlet, but the standard ECU won't like it all that much. Exhaust manifolds, use the MPI (tubular not early cast) exhaust manifold, reweld the tubes to the flange round the outside, and then grind out the excess weld on the inside, the cylinder head can be lightly ported, best gain is from cleaning up the joint between the machining by the valve seats and the cast port behind it, and making sure that the short side of the ports turn is 'clean' of lumps and bumps. Early K-series (top hung liners) are much more robust than later (with the advent of the 1.6/1.8) versions, so use that if you can (and don't want the bigger capacity)- all 16v SPI are early engine - to loose weight you can use the plastic manifold, with an adaptor to use the metal throttle, VVC manifold isn't worth while on a 1.4, the twin webbers that Caterham started with gave no benefit over an MPI inlet, so don't go throttle bodies unless you take the level of tune a lot further, as the 1.4 is short on torque in standard trim, much over 130 bhp (Caterham supersport) will end up with a slower car, and the revs need to be used, even at that power Caterham found the car to be slower on a circuit if they kept to the standard rev limit of 6,500!