You will only see that higher voltage if you are forced induction or the gap is very large otherwise the gap determines the voltage - the bigger the gap the higher the voltage. The higher the compression the higher the voltage. The MSD is going to help if the mixture does not ignite on the previous multiple spark during each compression stroke giving it more chances to ignite the mixture.
When I ran one in my 65 Rambler Flat head 6 I had gaps in the 0.080 inch size and on wet days saw 2 inch sparks off the spark plug boots to the head.
So, the load determines the voltage? I'm an electricity noob. I have high compression, and increased the gaps to .06 over. When I was determining the biggest gap I could get away with on a travelling van, I'd increaes them (at night in the dark of the desert) until I saw the arcing, then I'd back them off a couple thousandths, until it went away.
The I made sure, by licking the leads.
EDIT: I thought the MSD box also gave a bigger initial charge to the coil.. 400v?