MS2 will do your fuel and spark(if you want it to). Nice thing about having the MS do your spark is you can run more advance at idle, yet have it retard timing during cranking. Plus extra timing during cold start warm up, etc. Not familiar with what your holley system all does but I would consolidate it all into one system if I were you.

MS2 is batch fire, which would be fine for 99% of street users. Edelbrock sells two different port EFI intakes as well as fuel rails so your fabriation needs will be minimal.

If you don't mind the look, you can weld a sump onto the bottom of your tank and use a walbro gsl-392 external pump. I think those will fuel to about 550-600hp if memory serves.