In looking at the Yamaha spec sheets for the 1975 TY175B and DT175's, the DT has a slightly higher compression ratio. The DT175 head has 2 spark plug holes and appears to be the reason for the higher compression ratio. Could I find a DT head to simply raise the compression ration on my TY? That way ...

You say the DT175 has a longer pipe over the TY175, does the shorter head pipe create more toque than a longer head pipe? You can now buy both "standard stainless" and a "longer" pipe? I'm confused? Normal state of mind.
Rod

Probably a stupid question but...in the picture of the disassembled forks. The springs have one end tighter wound than the other, does it make any difference which end goes up or down in the fork tube? I was told at one time the tighter wound end goes down.

My timing was set closer to TDC than the 1.8mm setting and it did run but backfired and had very little low end. When I figured this out I set it at the factory setting and it runs much better.