Which are the engine rpm of the 1972 amc gremlin ?

The 232 cu in (3.8 L) I6 engine that was optional for 1970 became standard, while a 258 cu in (4.2 L) version became the option. compresson dropped from 8.5:1 to 8:1 for 1971, resulting in 135 hp (101 kW; 137 PS) (gross) from the 232 cu in (3.8 L) and 150 hp (112 kW; 152 PS) (gross) from the 258 cu in (4.2 L)

120mph

You might be able to find a manual on this site.

https://www.manualslib.com/

You can acquire this manual from most any PepBoys store. If you'd rather, just type in your google box "1977 AMC firing order".
Naturally you'd put the engine size,6 or 8 cylinder with displacement, right after AMC in your typing. When you click the search button it will show you your firing order. Google is your friend.

in the heater box eather under the passenger side of the dash or right hand side of car at the firewall

Spray oil the bolts at the back end of the straps and let set for a while. Then remove the nuts securing the tank straps to let the tank down, remove the hose and gage wire from the tank and pull it out.

Easy fix. Buy a MATCHED SET of cam and distributor gears. When you replace just one they don't mate correctly. Break them in with either white grease or engine assembly lube. Run for a couple days and pull the distributor out and look for correct wear pattern. It should be in the approximate center of the gear. I drag race a 72 Gremlin with a 401 that turns 7400 RPM. I use this method. No gear failures as of yet. Also, there is an auxiliary oiling kit you can buy to run additional oil to the gears. Any of the AMC racing parts distributors will have this. Check the net and ebay.

I have a 72 amx, the two wire conector at the brake light switch down on the brake pedal is light green and pink and the plastic connector is brown and plugs into the switch at the top of the brake pedal.