For what you are tryin to do based on those pics and that turbo you need both. Match your pump and injector sizing to the hp capability of the turbo.
You can use the ECU GN or you can run an MS3 plug n play to run that combo. Auto tune will be your good friend. I would suggest a coil on plug...
They can do the three bolt exhaust housings to fit the Buick. The last 58/58 I bought from them I had them use the stock exhaust housing. They were having a hard time finding those to build them. 4 bolts are no problem.
A paper element fuel filter will compress inside under pressure and cause a restriction.
You can run a stainless mesh filter with a 100 micron filter and solve that problem. You can even run it in the same location where the stock filter is now and it will fit. We are being told to run two...