The trail head might have been up Branch 31 - up above where the West Bay Hotel was located. If you are an old timer like me, you will remember when (pre 1972) the highway to Tofino was not along the lake as it is now. The highway was actually the MacMillan Bloedel gravel logging road half way up the mountain. You would climb switchbacks to about a mid-elevation along the ridge above Sproat Lake and then eventually descend to the lake level near the far end of Taylor Arm on Sproat Lake and proceed to Tofino. I used to regularly circumnavigate Sproat Lake without touching pavement back in the day. The road was somewhat de-activated but I managed to get through - some of the bridges were dicey.
I've done a bit of riding along the southern side of Sproat Lake these last few years and many of the roads have been removed to put things back to their natural state. Hell, I used to take my TL125 up into the alpine areas and ride on top of the frozen snow crust in the wintertime. This was my playground back in my '20s.