Indy heads single water crossover /single plane manifold.
The bypass is only needed if you’re running a T-stat.
You could pull the stat...... no bypass needed.
Or you can drill like 6-8, 1/4” holes in the t-stat flange to let coolant flow past/though before it opens.
Yes, it will take longer to reach operating temp.
The plus side is that when open, all the coolant passes through the radiator, instead of a portion of it being recirculated back into the engine without making a trip through the radiator.
Not all stats will accommodate the drill mod.
It needs to be the type with the wide flat flange.
It also obviously increases the overall flow capacity.
As mentioned, the timing situation really needs to be addressed.