A weber DGV type carb from say www.webercarbsdirect. But NO so such thing, I have no money. Then no carb.

Also Im going to assume your L20 has the heater plate type intake that uses the exhaust man to heat the intake manifold.
The SUs would use a water line system so holes have to be drilled in the head to heat the carbs(for winter driving).
The EZist would be a weber but if stock works right now just keep it if cost is going to be a issue.

A '78 510, if stock, doesn't use the heater plate intake. A W58 head has the water circ system. But it also has that nasty round-port smog exhaust that makes installing a SU intake impossible (the air gallery gets in the way).

A Weber DGEV with adaptor is the cheapest way, and they can be found on eBay for various prices. I got a brand-new but opened (still complete) Redline kit for under $150 shipped. Used ones show up for around $75 all the time, but most need rebuilding.

The only drawback is if he lives in smog-testing area. Most States that have testing, a '78 has to be tested. Washington, it's testing exempt for now.

Actually no this engine that is going into the car actually has a head that has the square no steel liner head on it. What about SU's are they any good? maybe after market?

Federal EPA regs are a gray area- States can test vehicles as far back as 1968 (when Federal EPA emissions regs went into effect). California tests back through 1974. Washington has a history of moving the year around. In the 1980s is was all cars under 12 years old, every year. That exempted my mom's '73 620 for 2 years ('85 and 86) but in '87 they changed the law to all cars 1968 and newer every other year. In 2001 they changed the law to all cars between 5 and 25 years old. If the EPA gets more funding there will be more pressure to increase testing again, perhaps expand testing to several other counties.

If the EPA finds that a regions air quility has got worse, they require the region to enforce more strict testing. Since the Seattle area has actually got better, they won't require testing of cars older than 25 years. Even then, they still might not. In CA. the older cars that did not need testing any longer were becoming more desirable to keep, hence more people kept their cars longer, so they didn't have to hassle testing it. Now they send more cars to the crusher than every other state combined!

The testing company contracts take this into account, and since it's the local authority that pays, not the FED's the state has to fund it. And it would be hard pressed to fund something that isn't need or dictated by law.