Hi Len,
I don't have quick answers for you specific to your car. Hopefully some others will. Here are some generalities to consider:
The Weber will likely be the most expensive setup of the bunch. If I were going that route, I'd want one throat per cylinder, so that would mean two DCOEs on your car.
Yes, the ideal is to tweak Webers for altitude and different atmospheric conditions, to get the last little bit of performance out of the engine. However, truth is that might be done on the race track where a half second lap time is a big deal, but for the street it's probably not often done. I ran my TR4 all over Colorado with DCOEs for years without changing the tuning, once it was set up. That might mean a slightly rich mixture at the top of a big hill, or a slightly lean mixture in some other circumstances, but it's not a huge variation in most real world street driving situations. Go slightly undersize on Webers for a bit more flexible street performance (slightly smaller venturis than a racer would use for peak rpm tuning, with jetting that's balanced accordingly).
One thing the Webers bring to the equation that neither the ZS or SU will is an accelerator pump. That will help with acceleration, but probably not fuel economy.
Just fiddlin' around with a pair of Webers to get them in tune is often frustrating and ends up being expensive. Better to put the car on a dyno, do it right, do it once and be done with it. That's what I'd recommend.
If you ever do want to tweak Webers a little, it just means having and extra set or two of some key jets and swapping them when you feel the need. It only takes a few minutes to completely swap mains and air correctors, for example. Webers are designed so that all key jets are very accessible and easily changed. Of course, you can get carried away with this and end up with a box full of various venturis, jets and emulsion tubes, if you really want to take it to that extent!
SUs might be my choice for the easiest all-around arrangement to work on myself and maintain. I'd look at a pair of smaller carbs, rather than a single one, if not restricted by racing regulations.
There is nothing at all wrong with ZS. They have about the same performance potential as SUs. It's just that there are fewer needles to choose from, service parts are a bit harder to find and the carbs are a little more difficult to work on.
Both SU and ZS are more likely to get out of tune and require some occasional attention, than Webers. That's because nearly all the metering of air and fuel in Webers is done with fixed jets and there are fewer moving parts and less to wear over time.
Depending upon the year of manufacture, your ZS carb might have some emission control limitations, may have little or no shade-tree adjustability and might even be sealed against "tampering". There were both ZS and SUs with some weird features that generally aren't good for performance, such as an anti-runon valve in the butterfly plate. So, a swap of carb models might do a lot to improve performance. Watch out though if you have to pass an emissions inspection with the car!
For that matter, Weber DCOE are not street-legal here in Calif., I don't know about New Jersey. And, of course, I'd certainly never encourage you to do anything illegal!
A carb swap by itself, without other matching engine improvements, won't give all that much performance boost, might just get the car back to where is was when the car was new and the carbs were in top working order. You really need to add a hotter cam, perhaps increase compression, do some porting, install headers and a freer flowing exhaust system, etc. before you will start to realize the full potential of the carbs. Of course, some of this can be done in steps and a carb swap might just be the starting point (they would need re-jetting/retuning once other mods are done).
p.s. Yes, I'd forgotten about PRI. I've seen their one-carb-per-cylinder setup on a GT6 at a car show. It looked really neat and sounded like a demon! I didn't get to drive it or even a ride, though, so can't say how well it actually performs. It seems like it should really go, though!
https://www.prirace.com is their website
Hi Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
