The picture will show what bolts need to be loosened to move the dist. That bottom picture that JMOR posted shows both bolts well.
If you want to get right down to it 8 deg btdc is wrong. It is really suppose to be 4 deg btdc at 450 rpm. The advance system in the dist will bring it up to 25 or 30 deg btdc when you get the engine running over 2000 rpm.
I tell people 8 deg to get it started because some of these old tractors will not run well at 4 deg. Once you get it running we can see if you can get the rpm low enough and set it at 4 to see how it runs.
Now I have to agree with JMOR. I am going on the assumption that you have #1 at tdc on the compression stroke. If you do not; or you are not 100% sure if you do; we need to stop right here and make sure. You can make things a lot harder on us by moving the dist when it is correct now.
Take the spark plug out of #1 cylinder. This is the one by the radiator. Stick your finger in the hole and bump the motor over till you feel/hear a puff of air. We are now comming up on compression. Now move the flywheel with a screw driver till you get the timing marks between TDC and 8 deg BTDC. When you get to this point your rotor should be pointing to the hole in the dist cap that you have the #1 wire installed in. If not rather than removing and turning the dist just move the plug wires around. If it is between two wires loosen the two bolts and turn the dist a little to where it points at the a wire hole.