87 formula with '73 400 4bbl
 

My roommate and I just picked up an '87 formula with a 400 4bbl and turbo 400 trans out of a '73 Catalina. As near as I can figure, the engine is pretty close to stock with the only deviations being an edelbrock dual plane intake manifold and maybe the carb (holley 4160, 600 cfm). Compression check found about 145 psi of cylinder pressure, and the smooth idle indicates a stock or nearly stock cam. The problem I am having is with the timing. I used a piston stop to locate TDC compression stroke so I could make marks on the balancer to use to check timing, so I know the marks are correct. The car will not idle below 900 rpm and will not run at all with less than 25 to 30 degrees BTDC initial timing. Every time I get the car running and try to retard the timing to where it should be, it just dies. The way it is now, it has too much advance and knocks from detonation. I have timed several engines in the past and never seen anything like this. Any ideas on what might be causing the problem?