Car won't run past 60mph

No 2.25 duals straight through mufflers X-pipe with manifolds. Unless those 318 heads are really just choking it down so much it cant go any faster. Small valves, horrible ex-ports, 973 smog heads, on a 360 bottom end.

It would be interesting to hear this thing running if possible.
I just have a feeling it doesn't run as good as you think it does.

How fast does it get to it's apparent top speed from a stop?