I'm helping out a neighbor with his 68 vette and have run into several odd component info that I would like some help with

Camaro guy only here. Trim tag: Chev L03 Trim ZQ4 Paint 972. The car has been heavily modified in the distant past with stinger type ZL1 hood and side pipes etc. It also is a ragtop with a roll bar? It was purchased back in the early 80's by my neighbors father, since deceased. The car has a curved neck radiator (looks like a 4 core) Harrison with a tag of MK 9 301880. It has a M20 Muncie partial vin stamped to the car. The block in the car is a 010 cast C119 with a block pad stamp I've never seen before? It reads 111539630K 04 22 CGC....yes its that long!! I could not find a partial vin at the pad or rough casting unless this number is it? Other trivia includes non booster four wheel disk brakes with a DC master. It is also non power steering. Edelbrock intake and Holley List 3310-2 carb and mallory ignition. It also has a 3/8th inch fuel line with a return that is curved up at the tank and unattached? Again, not being a vette guy I'm hoping for some guidance as to how this car was factory built. Its a great looking solid car, Thanks