Compared to the factory two barrel intake the Performer and Holley probably gained you about 10-12 HP
The only advantage of the standard Performer intake over a stock 4 barrel is a weight savings of about 22 lbs.Your '71 was one of the first years for smog motors with retarded camshaft timing and the crappy Thermo bump heads and dual diaphram retard distributors.The best thing you should do is is address these issues with a camshaft change and better heads and ignition.So lets start here:Six Budget Ford Heads That Work - Car Craft Magazine
Since you stated on another post you mentioned you still wanted good mileage so actually the best priced Flo-Tek heads could work in your favor keeping in mind the weight of your car it takes torque to move weight so this is my suggestion for a camshaft:http://www.summitracing.com/parts/hr...view/make/ford
I have it in my cruiser the bottom end and mid-range is very good it will pull up to 6,000 RPM no problem with the RPM intake I have your Performer intake will still have good low and midrange power.The weak link in SBF Fords is getting them to breathe, so the extra exhaust duration in this cam and better heads will help you with your goal for a distributor that is reliable and budget friendly and EZ to hook up go this route:http://www.summitracing.com/parts/sum-850022
all it needs is a 12 volt source and it's a done deal.Now let's address the advice given above,for up to 400 HP the later roller blocks are OK above that it gets scary your '71 block has more beef not as much as the prefered Mexican block but it will get the job done.Camshaft break in is critical with a flat tappet hydraulic as opposed to a roller cam but that is easily addressed.With the better heads and Cam you will need headers to enhance the package.