I have the Truck Avenger 650. I have to say Holley did all right on this one. I haven't been a fan of Holley for off roading vehicles for a long time now, but when I couldn't tune my Edelbrock for emissions, I switched to Holley.
I had to install smaller jets for the elevation change and now it works great. Passed my emission test with no problems.
I can feel the difference in the low end and hi-way passing power.
On the 79' CJ5, 304 engine I had years ago, I installed a 500cfm Holley. It worked great, but it would never pass emission.
Go with the 650 cfm . Even more so because of the headers.
You don't want to under feed the fuel. Pings, spark knocks, burnt pistons, etc, etc.
Good luck with your project.
80' CJ7, 360 Howell Injected, 3" single exhaust, NP435 4spd, Dana 300 AA clocking ring, Currie twin stick, Tera-Low 4 -1 kit, Dana 44 front, cut 10" wider to 63", 4.10 gears, ARB, Yukon axles and Super H/D u-joints, Currie Dana 44 rear, cut wider to 60 1/2", 4.10 gears, ARB 35 spline, Currie 35 spline axle shafts, 2 1/2" x 11" Ford drum brakes, CJ-SOA conversion, Tom Woods F & R drive shafts, Warn 9500i winch, 6 point cage, Homemade F&R bumpers and tire carrier, 1" body, Pro Comp supension Kit, 12.5x35x15 BFG's, 15x10 OMF beadlocks, Body armor, OBA.