Distributor installation is rarely easy with a Ford V-8. Your goal should be rotor indexing at No. 1 on the distributor cap. You must also have No. 1 piston at top dead center with both valves closed (compression stroke). Getting the distributor to seat is the rough part. Index the rotor just ahead of No. 1 and wiggle the distributor into place. If it won't seat, gently bump the starter or hand turn the crank. The distributor should fall into place. Crank the engine around to No. 1 compression stroke again and make sure the rotor is at No. 1. Remember, No. 1 can be just about anywhere you'd like it as long as you have the correct firing order.