pick up the 3 235 rochester on ebay from $1-30 bucks a peice from variouse sellers, rebuild them for about 20 bucks a peice. you could use Carter W1's if you got the 216 manifold, it will bolt up but the bolt spacing is diffrent, which is the Carter W1's bolt spacing. as for fuel mialage, if your driving at like 50-55 MPH and only 1 carb is open, your only using 1 carb, as u go faster your efficency will naturally drop. progressive linkages can be bought but are not hard to make with some steel rod, a thread die for that size rod anda couple plates u can cut out, I like the 1's that use the center carb as the carb that is the main carb ( put the choke on this 1, all others have no choke ) and the carb that opens first, for fuel distrobution, it's smack dab in the center just as the original was. only problem is keeping the carbs tuned in right, but u can get a balance bar from www.speedwaymotors.com to tune them in right, it's not gonna affect the cars reliability if there out of tune, your just gonna know it. www.stoveboltengineco.com has everything you need, and it's 1 guy that runs it, Steve Langdon he should be able to answer any questions u may have. I do know that Fentons will work with the offenhauser intake with the fenton heat riser kit, what u might want to do is have your factory exhaust manifold split into 2 exhaust, then u can run the offenhauser intake with no problem cause it will sit on the factory heat riser, just like the original. another thing you could consider is a 2bbl from stoveboltengineco, he sells Holley/webber 2bbls for like $89 each, you could get 1 of these along with 1 of his 1-2bbl adapters he sells to fit these on, bolt that up to your factory intake, run a split manifold and go cruising, that's a little less complicated than most options. you will need an elecrtic fuel pump in any case due to the fact, the 3 1's will require more GPH of fuel, a 390 holley needs 6-7 PSI of fuel and your stock mechanicle is pumping out 3.5 PSI, and the holley webber needs around 4-5 PSI. also need an ajustable regulator. the pump can be put after the original pump or eliminate the mechanicle pump with a block off plate.