Lockup for 200r4

[tdangle]

OK, I searched and read so many messages and articles on a 350 to 200r4 swap that I am overwhelmed.

I'm picking up a 200R4 to replace my tired and leaking 350. I understand the TV setup and have no problems with that. The area that I'm not quite understanding is the lockup functionality. I've looked at the kits which seem to be a little on the expensive side for what you get. My main confusion is why do they replace the TC Lockup solenoid? and what function does the 4 gear pressure switch perform?

From some of the wiring diagrams I have found it looks like if +12 is applied to the A pin then the TC will auto lock in 4th only. If you apply + 12 to the D pin the TC will manually lockup (I assume 2-4) Some of the messages/articles I've read is this is all you really need to do. (of course a low vac and brake switch needs to be incorporated)