Slant 6 stroker?

IF and only IF I were wanting to do a \6 turbo I'd just CNC plasma or water jet cut 6 Stainless Steel flanges and weld some thick wall tubing up to a T4 flange. This way you can match the firing order for a split 3 + 3. The T4 turbo has twin scrolls so plumbing 3 into one and 3 into the other will be best.

But if its not being done for pure looks and I really needed a 6 cylinder, I'd just do a max build on a 3.9L V6 with a hairdrier on it with maybe 10 PSI. Yes the ports on the 3.9 suck but on each head, max port the bad port and then flow match the other 2 to it.