Hard start...

Step back and go back to basics

When the ignition switch is in "run" you should have anywhere from 6-10V at the coil. Full battery means the ballast is out of the circuit OR THAT the ignition box is not pulling current, which it should be. Lower than 6 means poor wiring connections or some other problem such as a bad ignition switch itself

When the key is in "start" the coil plus should have close to "same as battery," meaning if that the battery is pulled down to 10.5 when cranking, then the coil + should be so.

If one or the other of those is not true, it's right there in that immediate circuit, from the key switch IGN1 / IGN2 terminals, through the bulkhead, and out to the ballast and coil connections.

YOU SHOULD BE able to jumper 12V direct to the coil+ for testing and get it to run. If not, you may have problems in the ignition system, whether wiring, connections, a bad coil or bad ignition box.

THAT IS what I would do FIRST, get it running on just the basic system since you can't seem to figure it out.

EDIT see very bottom of post

With power jumpered direct to the coil, a test gap at the coil tower, and cranking the engine either with the key or by jumpering the start relay, you should get nice fat rhythmic sparks out of the coil

I saw your message. So is this a "big cap" HEI with the coil in the cap? In that case it gets more simple. You have ONE power wire feeding the HEI

You say "the two browns" but see I don't know what that is. You need to ID the brown (if it IS brown) that comes from the IGN2 on the key. This is hot in start/ crank just like the yellow "start" wire is hot in start

You need to id the IGN1 wire which is hot ONLY in "run." Connect those two together and connect both of them to the power feed to the HEI

With modified harness/ wiring, it is impossible to talk colors, unless we know that what you are referring to mataches OEM. If not then you have to go clear back to the ignition switch