Chevy350 problems

[Chevy 350 Fan]

Hey guys I'm a senior in high school and have a 72 GMC truck I'm restoring after it burned up. Anyways I scored a sweet 500 HP Corvette Motor for it. It was built in a race shop in Texas. Obviously I didn't buy it new. I bough it from a buddy I have done business with before he had it in a mudding jeep. he said he hasn't put many miles on it. Anyways I went to start it for the first time and its really trying to run but only header tubes 2 and 4 are getting hot. It has a dual plane intake so I don't think its fuel as its sucking gas and air from both sides of the carb for 2 and 4 to run. Another important detail is he told me to follow the firing order on the distributor cap. Its not the typical Chevy firing order.
1 8 4 3 6 5 7 2 is the good ol typical Chevy firing order.
1 8 6 2 7 3 4 5 is what the cap said and he told me to use
now if its supposed to use the traditional firing order one would think 2 and 4 would line up but as you can see they don't. I'm running a MSD 6AL rev limiter/spark controller. I'm really lost here any advice would be much appreciated.
Thanks!