Twin 45s on a 90hp tune? Way overkill. You’re just going to lose bottom end. Frankly, with 9:1 pistons and a mild cam, just stick with the two barrel downdraft. It’s a good torquey set-up.
What are your valve sizes?
I have a medium tuned crossflow (11:1, largest stock valves, mildly ported, fast street cam, header and twin 40dhlas). I happily run Bosch WR5DP plugs. The recommended plug is a W5CC or NGK B7ES. The DP plugs are expensive but they resist cold fouling better.