How to break in a new fuel injected engine?

New engine and unknown fuel system is a tough situation. It'll fire it up on the stock system, but how things will behave even idling is the big question. With a cam in this thing disrupting manifold pressure vs a stockish cam, I would expect the stock FI system to be somewhat whacked out so that's a crapshoot with a biggish cam. I don't see how just changing intake manifolds will make any difference to the cam situation. Maybe someone has tried it here and can attest to the results and say what cam they had.

Do you have a known running carb and intake set-up, and a stock distributor and ignition system? I'd use that for the initial cam break-in so you can get through that most critical phase without starting and stopping the engine. (Once you are through that, then all that is left is maybe some final ring/bore wear-in.) You could even do some heat cycles and driving around on that setup 'til you get the EFI system ready.

If you're gonna drive around on an unknown tuning setup of any type, I'd want to have an AFR gauge on it to keep an eye on the mixture. So you ought to consider adding one, IMHO. (Just keep in mind that they will read abnormally lean during the first few minutes of engine warm-up.)

BTW, that lbs per hour limit on the stock injectors will mostly come into play at moderate throttle or WOT. FWIW, if your new setup will have an adjustable fuel pressure regulator, you can play with fuel pressure adjustments to compensate somewhat for that.