Mechanical injections were designed for racing only without a lot of consideration given to how they might perform at mid range cruising. Over the years we have sort of semi perfected the idle and mid range compared to the way they were in the "old days"
Algon's and Pete Jackson's are dinosaurs, and good for looking at on a Rat Rod but they are too complex and temperamental.
Hilborn is the best running , but Enderle is just as good , just lesser known.
I recommend a 1- 13/16 " 2- 1/16" 2 3/16" or 2 1/4" for SB Chevy purposes, not a larger one , unless it's a 406 cu in or larger . For a Big Block engine , you will want a 2 ¼” for a small 396- or stock 427- , a 2 7/16” for med size engine , and 2 5/8” to 3” for race engines 460 and larger .
Here is my recommendation. If you plan to drive it about 500-2000 miles a year, and don't have a giant expectation of cruising along at a loping 50 mph in high gear at 2000 rpm very much, then a mechanical injection it may be fine for you.
If you want and expect a instant warm up, get up and go, and drive in much traffic , and expect it to be something other than a Hot Rod , you might want to consider a EFI Version of the Hilborn or Enderle. EFI is a converted or new electronic version, and looks pretty much the same , but will do the things that mechanical injection is deficient in.
I can put together a full mechanical system for you in a price range between $2300-$4000 . $2300 being a manifold that is nice but not super show, a used pump, filter, shut off, by pass and secondary valves with instructions ...... In between could be moving up to a NEW fuel pump for an additional $300 , and from there , we do things like better filters, shut off valves etc for an additional $200 ....so , say $2500 total, and you only have to fab some hoses and linkage.. Then depending on the engine, a different refurbished manifold might be another $300 more and then a package with all NEW equipment totally can move the needle to about $3200 with Enderle and $4000 with Hilborn .
The pump can be belt driven from it's own belt drive which doesn't interfere with your water pump etc or cam driven which will require moving the water pump,, which I don't recommend on the street.
It will start, idle pretty well, have a choppy mid range when not under power, and run like a scalded dog , as well as look Bossy.
Now - Efi ( Electronic fuel injection )
All mechanical manifolds can be converted to EFI- the conversion can run between $1800-$3500 depending on who does it . $1800 might be you doing it by buying the parts from Mega Squirt or someone else on the low end .... $2400-$3500 would be one of several folks who convert them, and depending on a ton of factors can take from 10 days to 3 months to accomplish it . There is no assurance beyond their promise of what you might end up with, but there have been many successful conversions, also some unsuccessful ones.
I am a Dealer for the Factory built Hilborn EFI units - Hilborn pioneered this manifold, and they make a great product. Prices run between $5500-$7400 depending on the ECU chosen, use as well as the air filters you choose. We can also powder coat the manifold any color or polish it for an additional $400-$600. It will start and run as a daily driver, and have unlimited customer support . The new Holley Self learn software is better than F.A.S.T. or the others.
I would not be scared of a mechanical setup if you want a limited use Hot Rod ,,,,but EFI can take you on vacation if you choose to do so .....
Call me weekdays between 9AM-6PM CST at 615-483-6830 for more discussion.
ps..... there are no dumb questions, except the ones that you fail to ask :>)