Triumph Repair: twin carbs, british car club, poor gas mileage

Question
do you recommend any sites for the twin 1.5 euro carb? what would be an average price? My spitfire is also recieving poor gas mileage, i believe the oil level in my carb may be incorrect(any tips on getting the correct level); i am getting 15-19mpg! is there any way the fuel pump is pumping too much fuel into the carb. (fuel pump is not stock.) My car will also not go over sixty mph. It would just begin to redline. on one of my sparkplugs i will pull it out and the spark wont be as powerful as the others- but the sparkplugs are new. i have taken the engine block of and scrapped the carbonization off near were the sparkplugs are.thank you for your previous answers.

Answer
Earl, Are you asking about getting twin SU carbs? That is a common conversion and will improve performance. I doubt it will improve mileage much. New carbs would be very expensive, You would have a better chance of getting a pair of SUs with manifolds from someone in your local British car club or on E-Bay.
Something is very wrong now if you are only getting 15 to 19  MPG.
You can't get the RPM to redline in 4th gear at 60mph. If so your clutch is slipping very badly.

If you mean you have the throttle on the floor in 4th gear and it will only go 60mph that is different. If so you need to put a vacuum gauge on the intake and run the RPM up and read the gauge. If at high RPM it goes to zero, you have a stopped up exhaust (If you tested everything like I said)
If this is the case you need to first do a compression test. (dry & wet test), check valve clearance, set timing then look at the carb.
First remove the four screws in the top cover and inspect the diaphragm for tares or holes. To check the oil level in the top just unscrew the top cap and lift it up and push it back down. If you feel hydraulic resistance then it is ok. If it is over full it will expel the excess out of the small hole in the cap. It is just a shock to dampen the quick movements of the piston which acts like an accelerator pump and it dampens the pulses at idle.
If you see a weak spark on one plug switch plugs to see if the weak spark moves or stays on that one wire.
Let me know,
Howard