Sorry yet another towing wire harness 4pin/7pin plug question?

When buying my '12 prerunner, there were two options:
A port installed option, which is an added class III receiver hitch and a 4 pin (running lights, left turn-brake, right turn-brake, ground) connector, probably connected behind the tail lights harness. 3500 capacity.
Factory tow, installed during build, otherwise called the Tow Package with a class IV, coolers, brake controller interface, alternator/battery upgrade and 7-pin (adds brake controller, backup light and aux battery power). 6500 capacity
Prerunners in my area at least were never stocked with the tow package; don't know why but mid-atlantic toyota did it that way so I had to special order one. I was offered the add-on 4-pin on a vehicle on the lot, but decided to wait.
So if you want to run a brake controller, you can splice in a 7 pin to the 4-pin you have, if it will match the brake plug from the rig you want to control, and run at a minimum additional wiring as required to access the vehicle brake system splicing it into the appropriate wire on the new 7-pin. (Aux power and backup lights may not be needed...?)
I'd take the different approach; get a 4-pin plug to 7-pin female adapter, or make one w/o cutting into your wiring, and get help-lookup how to run the brake controller wiring by itself to your 7 pin adapter to the appropriate pin. May want to get help on this part to match up the brake controller module you purchase with the wiring. Below are current info s/b applicable to other 2nd gen
14 mech page from brochure.
14 pic from owners manual showing tow brake interface.

 

2015 PreRunner with Tow Package is rated at 6400# Port Hitch 3500# so they offer it now, I would assume it was offered in the past.

 

Here's a thought for you. The new trucks come with a 7 and a 4 pin. Why not buy this from Toyota and wire it up and have both pin connections. They will give you the info you need to wire it up and you'll have it set up for any trailer you want.