The listing is correct the bolt pattern is different. I used the 6114 on GT heads for years with no issues. The top bolt hole on the outside cylinders do not line up they are off about 3/8 of an inch vertically. Take a strait edge and lay it across the NON CJ heads and you will see the outside top bolts are lower. I also believe the bottom holes are non existant thus 14 bolt instead of 16 bolt. I used them they sealed fine with the right gaskets, there a few versions of the gaskets. Someone else will chime in All I can say is I used them for 30 something yrs. I have Ed Heads now and for the first time in 39 yrs I'm using 16 bolts.

just make sure you let the rocker go through its movement on the valve tip. It should stay in the middle of the stem or close to it.

Thats where the oil gallery is they require longer studs there.

look for cross bolted mains.

looks like roughtly 20 hp to me. I recently installed a 4 core aluminum radiator and twin electric fans. I need an electric pump lol. That would raise my very dissapointing 415 rear wheel dyno results a bit. Since that time I went to a 3 inch magnaflow exhaust, Which feels like 100 hp over the flowmasters. and an 850 dbl pumper from a 750. I will probably find out at Beaver Springs Fe reunion what the 1/4 mile times are.

Hot Rod or Car Craft had an article yrs ago. I think they said the X pipe was equivalent to running open headers or something like that. I showed it to an older muscle head  coworker and he was impressed by the results.

I found one similar
http://www.carcraft.com/techarticles/exhaust_system_installation/

Thats 15 minutes from my house!

I would go for the one with the bosses. Unfortunately your getting close to the 500 dollar Meziere. For the extra money you dont have to make all kinds adaptors to mount your alternator and power steering. How much HP do you think an electric water pump frees up?