Need help reverting to older library

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I am having trouble linking ploplot resulting in this:

dyld: Library not loaded: /opt/local/lib/libshp.1.3.0.dylib
  Referenced from: /usr/local/plplot/lib//libplplot.13.dylib
  Reason: image not found

I believe this is the shapelib library and that it is used by plplot but I now have a newer version:

$ port installed shapelib
The following ports are currently installed:
  shapelib @1.5.0_0 (active)

So here’s the problem. Some time back I wrote the Ada bindings to PLplot but there hasn’t been anything to contribute for a long time so this work has laid quiescent during the interim even though I use PLplot in my own work, apart from developing the bindings. My PLplot build is not through macports but my personal build from source that I made as a developer. I’m not very good at mucking around with these things and I don’t want to disturb (that is, re-build) that old build which works fine. I’m basically afraid that if I touch anything that I’ll have a couple days of grunt work to fix it.

How do I revert the macports installation of shapelib to libshp.1.3.0 so that I can link against it?

Thanks,

Jerry