I have a 351w from a 69' Mustang with gt-40P heads and I just can't seem to get it to run right. I am running a mild cam that was put in by someone else so I don't know the specs and a truck avenger 670 de-jetted to 60 primaries and 72 secondaries. I have a holley electric fuel pump regulated down to 4.5 pounds. I am running autolite spark plugs with a .45 gap and MSD 6 ignition, rev control anmd 8.5 wires. It runs like crap. I thought I had it tuned perfectly before I started running the buggy, there were no misses and it ran at 160 degrees with no problem. Then I put in the shafts and started driving it and now I have some problems. For starters, at idle it sounds like it's dropping about three cylinders. First I thought this was a vacuum leak but I only have two vacuum ports out and I have replaced the intake manifold so it's not that. I checked all the plugs but have not replaced the wires because none of them looks bad. When dropped into gear it drops so low in the rpms as to barely stay running. It stutters badly at takeoff but will run like a champ once it gets over 2500 rpm in forst gear While running any stab over the throttle is met with more sputtering. When shifted into second or third(c-6 with manual valve body) it just sputters all over the place unless it gets over three thousand rpm's. If I put it in low and try to power over something it just won't go.The msd is a second hand unit but I have tested it according to MSD and it seems to be fine.It's also running at about 190 to 200 with a 160 thermostat but that may be because it's over 100 out and I have a high flow water pump and a regular thermostat instead of a high flow. I had the carb tuned by someone who is supposed to be a carb expert but he could have put bananas in the secondaries and told me it was right and I wouldn't know. I have started thinking I may have a stretched timing chain as the timing has always been erratic since I got it running. I seem to recal when I had it on a stand that one side of the chain was tight and the other side had noticeable slack in it. I would rather not pull the entire front of the buggy apart only to find out it isn't the chain.The motor was given to me and I don't know enough about motors to have checked things like the timing chain when I put it together. Anyone have any thoughts? This buggy is ready for the rocks if I can just get the motor running right.