You could use it for a rough guesstimate but considering the time and expense that goes into LF shooting you might as well bite the bullet and get a good spot meter now.

When I was green I once did a studio shoot with chromes alongside digi and used the digital camera meters setting for the film camera.
When the film came back I was screwed because the dslr ISO settings (Canon) did not equal the true ISO standard.
The Provia was all over exposed by about ⅔ to a full stop.