The key to making the GT17 work is to keep the pipe run short and no bigger than 2". You do not need a massive intercooler. I'd advocate using a small twin pass, no bigger than what you'd find on an R5 turbo, it is just not necessary (unless you want to look cool having something hanging out of the front). I've used a diesel van intercooler on both of mine.
Here is how RickyP did one:
Mapped by Wayne, with a decom plate, made 180bhp with a GT17.
Someone else then added a MASSIVE intercooler later, which was far too big. Laggy and unresponsive:
But gives you an idea from cold-side to inlet.
This is a 106 using a T25 rotated so the outlet faces upwards. It goes in and comes out on the same side of the radiator. The only issue with this one, is the cold side to inlet is 2.5" which I haven't replaced. But it comes on boost a lot earlier than it did before.
TBF, I probably prefer the outlet facing upwards. I run a GT2259 and it faces out of the bottom and it was mega close to hitting Wayne's rollers!
There's little or no way to avoid a long pipe run to the inlet, but keeping the turbo to cooler run short & narrow, with that turbo will pay dividends with a small cooler. Spoken from experience!