Alot depends on the engine...What type of cam do you have in yours? If you like the lope lope lope then you aren't going to like the webers....any exhaust leaks will drive you nuts.
They should be setup as follows...now remember these are the new ones so you don't have to change much.
37 mm chokes
4.5 aux. venturi
135 main jet
F7 Emulsion tube
120 air corrector
70 F10 idle jet
50 pump jet
000 (closed exhaust valve)
2.0 needle and seat
You will probably want to change the needles and sets...the pump jet may need to be a 55 but you start with 50 the idle jets a little large and the mains are a little small. The chokes should be ok. You will need to add fuel lines but if you don't do AN fittings that won't be much. I bet you will have to put another $1000 in parts to finish it and have jets and stuff set right. Remember jets sound cheap but you need 8 of each one
Getting them tuned is the hard part once done I haven't had any problems with them. I would suggest that if you are in an area that gets alot of dirt you steer clear of them....I run mine without filters because they are so restrictive. Also you don't want to get caught out in the rain...remember water comes in through the scoop...oh and they don't get crap for gas milage.
Horsepower...nope..I actually lost 6 now I don't know if it was the pipes or carbs but I picked up 40lb/ft of torque...my guess is the pipes...the change with the carbs is the instant a quick throttle response...my car raps through the rpm range now...I used to never hit redline...I can't punch it without hitting it now.
Matt