Headers with Vortec heads issues

[Sherman Snouts]

1971 C10 small block, vortec heads, th350, lowered.

I cannot seem to find a proper header that 100% works with my vortec heads. The long tube headers i have now fit fine, they dont contact the motor mounts, cab, ect. But it seems that they were made for a different head. The header flange covers up threaded holes on the head that could be used to hold the spark plug wires. But more importantly, the flange covers up the threaded coolant temp port on the passenger side head.

Has anyone ran into this problem/ does anyone know of a correct header that clears everything on the head? Mid length headers are also acceptable.

Thanks in advance!

(I am currently running FlowTech headers)