Copmuter was for staying EFI. Second hand carby prices will range from person to person but you could find yourself a set of 35DHLA dellortos or webber equiv. for around 300-400. The only problem with making your own manifold for an NA setup (turbo too actually) is that depending on how long your inlet runners are will have an impact on how the power is delivered and where abouts in the rev range. Extractors again wont be too hard to find, i cant remember off the top of my head if the CA20 exhaust ports are similar to the CA18 as you could then modify a set of CA20 extractors which are plentiful. I have a Ford Corsair that has the Ca20 in it and all i have done is fitted a K & N airfilter, a set of HiTech Extractors 4-2-1 through a 2 1/4 inch mandrel bent system, sounds quite nice and have a little bit mroe torque down low as well as more up high. All of that there cost me less than $500.