I have 350 and auto
Believe (been a few years since I looked at one of these applications) that locates it at the shifter so access it from inside but would suggest you by pass it and test. That will provide a go - no go answer making the process quicker
I manually bridged the selenoid. Not sure but this is next one in the path!
So you just by- passed the dash and neutral safety switch and not the solenoid.
If you didn't get a reaction from the starter that way then its likely not in the key loop or the neutral safety loop. Guessing you got the solenoid to produce a single click and not a rattle.