"H-pipe," X-pipe," or no pipe?

I have had the same Dr. Gas x pipe (3" in / 2.5" out) on my last two big block cars for the last 15 years.I love it and think their design is true compared to a lot of the cheap copies out there in terms of flow and sound.
It also creates a scavenging effect helping to pull the exhaust out(I am no engineer but that is what the claim is).
On your setup it will quite the exhaust versus without it.It will also raise the pitch of the exhaust note as well.
Run what fits easily if space is tight.