Sam, you really need an angle finder for this, Harbor Freight has them for like 6 bucks.
Skip, you know better than that.....
If you can get the known height at the front of the engine at 0*, then on a 24" engine (BBC) you would add 1/2", this equals 1* of deflection which will be plenty because you wont get it that close IMHO.....Sheez.

I think a Ford 429/460 is about 24" long also.

Don't do many Fords.

Didn't you take Geometry in High School?

A small block would be just under 1/2", it works out to about 7/16"

GT