To check it what you need to do is pull the #1 spark plug and rotate the engine so that the engine is at top dead center on the compression stroke.(#1 at tdc while mark on balancer is also at tdc on timing tab) Now pull the distributor cap off and check the position of the rotor. It should be pointing at the #1 terminal on the cap. It doesnt have to be dead on, a little either side of it is ok as moving the distributor one way or the other will correct that, you just need to be in the vicinity.
Only other suggestions I have is to go over the firing order again...I know it sounds simple, but many have screwed it up...as stated above..1-8-4-3-6-5-7-2. Trace each wire from the cap and be sure they go where they are supposed to. As far as the cam not picking up until 2500, thats normal. I have run that cam a couple times and it is a little lame until 25 then picks up hard. It actually needs a small convertor and gears. Maybe check the vacuum line to the tranny, be sure it didnt come off at the modulator. Good luck! We've all been there!
