Is the wreck on reclaimed land or submerged? If submerged, GPR would not... it's a terrestrial technology- hence the name (Ground Penetrating Radar). However, a sub-bottom profiler/ magnetometer combo, tuned correctly, could yield some very interesting results IF the wreck is deep enough to allow good coverage.
EDIT: from
http://www.numa.net/expeditions/november-1981/
"Her suspected hulk lies about half a mile above the Boothville high school on the southwest bank of the river. Note; the mag survey by Texas A & M shows her to be almost completely under the levee. It’s best to look during low water. There is a flat reef-like barrier edged with a small rock breakwater that extends into the river from the base of the levee for about fifteen feet. If you can walk this area, you can easily detect her iron mass, but can only pick up a piece of her from a boat running parallel to the breakwater. She is buried nine feet under the mud and could be very well preserved."
So, if the info above is correct, the wreck is too shallow for a sub-bottom profiler and submerged in water rendering a GPR useless. (Unless there is a way to pull the GPR on a raft over the site and some how filter out the raft material- not sure if this is possible or not.
Shallow water excavation seems the only feasible option IF
1) permits could be obtained
2) boat traffic is light enough to allow for excavation
3) lots of bureaucratic red tape can be cut and
4) funds could be raised (which I feel is very possible)
5) 25 other reasons I can't think of at the moment :-()