Making alignment/eccentric bolts and I'm not sure what material to specify as I'm not the best with materials.

Obviously going to be some steel, but how would I specify say a Grade 8 bolt steel?

ASTM A354, BC or BD

http://www.portlandbolt.com/technicalinformation/astm/ASTM_A354.html

.

Grade 8 bolts are typically made from SAE 4140 steel. Any machine shop will have pre-hardened steel in this grade that will be approximately the same strength as an off the shelf grade 8 bolts.

I though B7/Gr5 were 4140, and A354-BD/Gr8 were 4340 or a similar higher alloy, to answer OP's direct question.

http://www.americanfastener.com/technical/grade_markings_steel.asp

Grade 8 and A354BD are both alloy steel with Tensile >150ksi, Yield >130ksi, and A354 stipulates >14% elongation. From Machinery's handbook, 4140 tempered to 900F will exceed all of these requirements. 4340 @1100F will be similar mechanically, but is less available, especially as a pre-hard bar.

I didn't have time to pull a cert and see what actual properties of as-recieved material are, but they are typically right in this area for 4140.

I don't recall off the top of my head, but I believe the chemistry requirements for these types of fasteners are pretty lax.

In any case, as far as the original question, 4140 Q&T is your best bet, as it is what most shops are likely to have on the shelf.

Can't adapt one from a Corvair/Corvette/etc ?

http://www.ebay.com/itm/C2-C3-Corvette-Camber-Rod-Adjustment-Bolt-Kit-/350533242709

A buddy bought a set from a specialist and  the bolt head is "marked" with 4 lines all in a 180 degree arc, and ABW or BAW.
the eccentric plates fit nicely.

 

wildfire, he asked for Gr8, which I gave him. But for his application, I think the Gr5/B7 (4140 spec) is better, as it is likely to have less notch sencitivity, a good thing for a notched cam adjuster. Hopefully it will be torqued with enough preload to make a friction shear connection. Also, he could do as I have done; buy a larger Gr5 bolt from a hardware/car-parts store, and have it machined to spec.