Big Block Chevy headers. tubes are 2 3/8" dia. Collector outlet is 4". These were on a '72 Nova with a Chris Alston Chassisworks front subframe. Should fit '68-'72 Nova and '67-'69 Camaro using the Chassisworks subframe. Headers were custom built by R.E.F. Unlimited (over $2000 when originally built). $350. No text messages. 928-TWO79-4SIX09.