I might also consider a drop in fuel pump solution, as i don't believe the stock unit will keep up. I'd also skip the custom intake manifold as well, mostly due to cost, but partially due to lack of need. what are you looking for in specific HP output for an 'as delivered' 22RE turbo? that number would help some. maybe make the intake manifold/TB optional?
if your looking for 250-270, there's ZERO need to replace the intake. i also wouldn't bother with a tubular manifold at those HP levels. too many manifold failures with them, and I've seen some of the best SS manifolds built by pros i respect fail in pretty short order. id stay with good cast iron pipe fittings and make a log style header for the turbo, and set it up, if possible, to hook to factory exhaust, or at least factory location.
now, if your 'as delivered' goals are more like 350-375 HP, then the tubular manifold, and plenum-and-runner intake become much more necessary if you want to keep boost pressure under 30. it also means no current market exhaust will handle the air flow, and you'll need to consider a kit for that as well.
try and keep it simple, if possible. lets assume my Toyota truck/car already had upgraded exhaust, but in the stock location. if your turbo motor bolted up to stock location setup, this means your turbo kit/motor would 'drop in' with little hassle. and with the factory intake/TB, you don't mess with cruise/throttle control. if your selling a delivered kit, you want ease of installation. if people want a project, they will just DIY it. you want this to be doable in a day with two guys and a case of beer.
my real advice here would be to make and sell parts to DIY this, as i believe you will get more business. offer the kit if you want to, but the moneys is in the parts. i have read through to completion no less than 400 turbo car builds over on turboford dot org for the last ten years, 100 more on nato dot org, and done 4 myself, in progress of #5, and i can tell you the ratio here for 'home brew' vs. 'drop in' is about 40:1. very few people buy a complete engine, turbo and all, and drop in and go. turbo selection is very dependent on engine specs, vehicle weight, transmission, intended use, supporting mods etc etc, it gets complicated fast. what works for one car is useless in another and so on. and the same goes for almost every part in an engine build.
anyways, if you'd like to chat, i can put you in contact with enough small shops and home DIY suppliers of custom parts to get you all the information you'll ever need.
and if i have only one piece of advice, ONE thing if you ignore everything else ive said, PLEASE heed this warning:
DON'T SELL A PART YOU HAVEN'T COMPLETED, AND DON'T GUARANTEE HP NUMBERS!
in all the 'dealings gone wrong' I've read about, and the three horrible wastes of money and time I have dealt with, 9 of 10 are a direct result of violating these two policy's.
feel free to email me.
-J0N