Primary size and length on SC engine

Well this kind of stinks.
My math:

stock port opening at about -2.5"

1.75 primary = 2.14 x4=8.56
1.875 primary =2.46 x4=9.89
2.00 primary =2.84 x4=11.36
2.15 primary =3.14 x4=12.56
2.25 primary =4.15 x4=16.6

3.5 collector =9.08 (use 1.75 maybe 1.875)
4.0 collector =11.95 (use 2.0)
4.5 collector =15.20 (use 2.15)
5.0 collector =18.5 (use 2.25)

does this look close?
thus meaning run a min 1-7/8" tube or 2.0" tube to maybe a 3.5 collector but preferably a 4.0 collector.