Ughhhh man this is tough. First of all, the 3500k will veg a plant. But I would like the 3500k a lot better in a full cycle light, especially the vero 29 line. It seems to have just a bit more red in the spectrum than say the Cree 3500k which is what pretty much everyone uses for seed to harvest in that line. In my opinion, I would feel a lot better if you got some something a little more colder white for a strictly veg light. Just as a thought, have you looked at sourcing the chips somewhere else? And then just trying source the other stuff from jerry? Looking around, I see them under $30 a few places.
As far as the driver and sinks go, you could do that. But you'd really be getting away from the strength of the vero. Going from the hlg 320-2100 to the hlg-240-1400 means you would be running each cob at about 55 watts instead of the number we figured, 78 watts I think. That's why the smaller heat sinks would be good, less wattage.
All things considered, the setup he recommended would work fine. But you'd be giving up about 80 watts, and getting away from the strength of the vero cobs.
Does he not have the hlg-320 or 180mm heatsinks in stock? Or was he simply giving you a cheaper option? If he doesn't have them is one thing. If it's a savings thing, it was $2 or $3 extra per sink, and an the 320 watt driver is around $20 more right? At $35ish I would personally stick with bigger driver. Especially since you're going to be underpowered for the area even with the hlg-320. Even if it meant saving up for another couple weeks or whatever, doesn't really make sense to give up 80+ watts for $35ish. If you were building an 80 watt light using any other chip it would easily cost you $100 or more, if putting it that way helps. I'd try to get the 320 watt driver and 180mm heat sinks from jerry and grab the cobs from someone that has the 5000k or 4000k in stock.
And tell him to hook you up with the screws and wire anyway lol. The stuff is cheap, but I'm pretty they're 3mm screws and can be a real pain in the ass to find locally. I have no idea what he would send for wire, but worst case scenario can be scrapped. I like to use 18 awg mtw, rated for 600v. Its sturdy and durable, yet still kind of has a little flex memory. But there are lots of options for wire.