D-66 questions

So I did some further investigation (inspired by Rusty's post). I headed to the parts shed and pulled out a D-64, a Wieand Stealth. an LD340, a Holley Streetmaster, and of course, I've got the D-66. I miced the bolt holes and the thickness of the manifold at the Valve cover and engine center sides of the bolt holes for 3 holes. The result is that, like Rusty remembered none of these manifolds are made with the bolt holes perpendicuar to the mating surface, but the "normal" LA manifolds have bolts that are half the amount out of perpendicular, as the 64-5 manifold. Here's the numbers (all measured in hundredths of an inch) :
D-66 bolt hole - .42
All other bolt holes - .46

Manifold/ Short side of bolt hole/ Tall side of bolt hole/ Difference
D-64 .56 .69 .13
.52 .66 .14
.89 1.05 .16
D-66 .46 .53 .07
.46 .52 .06
.46 .53 .07
Stealth .50 .56 .06
.50 .57 .07
.59 .65 .06
LD340 .52 .59 .07
.47 .53 .06
.72 .80 .08
Holley .51 .59 .08
.54 .60 .06
.44 .53 .07

Now all I need is an actual engineer! Since you have to reach just beyond the bolt hole to measure the fat side, let's say the distance for a regular LA is actually .48 inches. The average difference in thickness is .07 inches. On the 64-5 manifold the distance is .44 inches and the difference is .14. Given all that, an engineer could tell you the angle of taper on a washer needed to correct the bolt head mating angle to use a 64-5 manifold on a 66 and up engine. I think you could then flip the washer and use any 66 and up LA manifold on an early LA. (you might have to correct the bolt hole angle in some cases, but not by much.)

OK so you guys know better than I who the whiz is that can give us the angle of taper for the washer and bring them in to this thread. I've found a few different sources for round tapered washers and they all seem to sell them by taper angle.