Slant six’s and Mopar Small blocks share the same stock installed height and spring diameters. In the later years the slant and the 318 shared the same valve spring from the factory. And 340 valve springs are a common upgrade on slants.
For my build, I am using 11/32 stem diameter Ford 289 valves, the installed will end up in the 1.600 range. I am needing springs that can handle .570 lift, with around 100 closed and 300 open for pressures. And I am wanting to use beehive springs.