The 67 is still a bit brighter than the Injector neck with these loads.
Reducing the load on the Injector neck with 500k pots won’t change its resonant frequency. I would instead consider an Area 61 and continue using 250k pots for a more traditional (less pointy) sounding response with the additional desired brightness, adjusting the heights of the pickups to help address the reduction in output if necessary. I intentionally chose the Injector for its warmer top end and output to keep up with the Fast Track 1 for distorted tones.
The exercise of swapping the pickguard for a vintage output set would be to determine whether the guitar was excessively bright, though I don’t believe it is. If it was excessively bright and I wanted the generous amount of chime provided by the vintage output set then I would use a brass block, perhaps changing out the saddles as well depending on the severity.
While the clean tones on this guitar are really nice, I’ll reach for a different guitar if I want the skinny Strat sound. As it is this guitar works well along side other guitars equipped with humbuckers. In a pinch I can plug straight in and get very useable Strat sounds without any adjustments. That’s the beauty of the Fast Track 1. It does an excellent job bridging the chasm between single coils and humbuckers. With the voicing I’ve applied and the values I’ve chosen for the tone control in position 1, it can get downright chunky with it rolled back yet still have enough output to be even with the rest of the positions, from the mid-bass through the low-treble without sounding honky.