Considering Holley sniper EFI for my 1969 340. Thoughts from people who have that set up?

Agree with Joe, the Tanks, Inc. ones are a really nice deal. I bought their tank and pump in kit form for my '68 Coronet, it was great. It came with a 255lph pump which was plenty for my application. They offer a larger capacity pump if needed but you'd have to be making some power to necessitate that. The EFI tanks by themselves are still under $300 and the 255lph pump is around $210. They also had brand new tank straps for like $15. have to get a sending unit too but they're not much. They also now offer floatless senders which are pretty cool but they are a bit more than the conventional ones.

The plumbing is where it starts to add up. As I've said previously, I use -AN fittings exclusively which add up quick but frankly I wouldn't use anything else. I have a surplus of them now but the initial investment can be eye opening, especially when you start getting into unusual adapters.

The one issue I can think of with the drop-in fuel pump modules is the plumbing and only in regards to accessing the top of the module. Once the tank is in, it can be difficult to deal with if/when you need to get at it since it's up against the trunk pan. I made short lines that connected to junctions just off the output ports so I could drop the tank without having to get at stuff that's hard to reach. Same with the wiring.

The baffles in the Tanks, Inc. tanks are fine. Again, I often drove the car until the fuel level was 1/4 full or less and never really had an issue. As long as you measure the pickup tube of the pump module correctly and ensure it sits on the bottom of the tank it should in theory always be submerged. If you run it low enough where it's not then that's really on you. A sump isn't really even necessary.