Cranks but won't start. Unplug ground at field spade on Alternator and it starts?

Voltage readings:

Battery at rest - 12.5 volts (battery is 7 years old)
Battery when cranking - 10.5 volts
Voltage at + side of coil when cranking: 8.5 volts (does not start)
Battery to + side of coil voltage drop from battery when cranking: 1.8 volts (does not start)
Battery to + side of coil voltage drop from battery when cranking, ground at alternator disconnected: 1.6 volts (starts)

Note the 8.5 volts does not match the 1.8 or so voltage drop. But I wrote the numbers down as I went and thats what my notes say.

Alternator spade resistance tests:

Spade that I ground to alternator body: 5.9 ohms
Alternator field with alternator ungrounded at other spade: 3.3 ohms
Old round back alternator, single spade connection: 31 ohms

Note: I have Edelbrock heads so not able to pull field wire off of spade on alternator unless alternator is unbolted due to no clearance no room to reach connector. And to unbolt alternator have to remove AC belt idler bracket, loosen water pump bolts, coolant runs all of the floor ect so unless I wanna go all out haven't removed alternator yet.