I just happen to have a 1977 Jag XJ6 that has two Rochester 175CDs on it, which I have rebuilt several times now, and I would suggest that you consider accumulating several 175 carbs to use for PARTS, and keep your original carb bodies as long as possible. The Main Jet is what usually wears out, and it can be pressed out and a new one installed quite easily. The only real difficulty with these units is that they tend to accumulate gum and rust particles in the float chambers and also in the inlet filters. When I first checked my carburetors, both inlet filters were almost plugged solid with rust. Also, both main jet bores were egg-shaped from the wear that the sliding needle produced. The pistons don't wear out on these carbs, they are centered by a chrome-plated shaft that I've never seen wear. The diaghram stiffens and gets holes in it, and should be replaced at least once a year - it's only a $5 part. Just make sure the passages are clear, and that everything is in good shape with a minimum of wear. The carbs were used on a number of vehicles, so finding them isn't usually a problem.
I haven't had any problems adjusting the carbs as long as they are in GOOD mechanical condition!
Best of luck,
'77 Jag XJ6L