Contemplating building a 4-speed transmission Options

[gms]

I am contemplating building a 4-speed transmission for the track that I race on most frequently. I know this sounds crazy but I feel I have good reason to do so. Currently once up to speed I only use 3rd and 4th gears (on a 5-speed) which is a diagonal cross plane shift. With a 4-speed I would just shift between 3rd and 4th gear using an S-(25:26)-3rd gear and a Y-(28:23)-4th Gear, this would be an easier straight shift between gears. The largest hurdle is filling in first 1st and 2nd second gears, I have an input shaft with a fixed A-(11:34) but then second gear gets into the unobtainium gear ratios.

I would like to find a B-(14:37) or C-(15:36) 1st gear fixed on the input shaft and then using an M-(22:29) 2nd gear would be feasible. Only problem is that I don’t even know if they ever made a B or C gear on the input shaft. Looking at the list of gear boxes I see that they made several 912 boxes with an E-(17:34) 2nd gear, that would probably work too. The F-(18:34) would just be too easy to stall the engine.
I am open to other suggestions except for an input shaft with welded on gear.

If you are not familiar with the 4-speed it is the same as the 5-speed with out installing a first gear. So every gear on a 4-speed is one gear lower when compare to a 5-speed.
Example:
4-speed 1st gear is in 5-speed’s 2nd gear position
And so on…