I have a crossover on my '68 C/10 Chevy pickup. [L6 292 w/ Clifford headers.] The configuration is more like an "N" than an "H" with a 45* angle cross tube between left and right exhaust pipes, after the collectors.
I had it done by Simmons Automotive about 20 years ago. Still works great. They're still there at Country Club and Irvington, in Tucson.

I/I #4101
'71 GMC Jimmy 350, sm465, np205,3.73 posi.
'68 C/10 Stepside 292 (.030 over) Offy Intake, 500 CFM AFB,Clif headers, sm465, 3.73 posi.
'67 K/10 454 project.
'72 K/5 rolling frame project.