4woody said

Here's a how-to make a shroud from fiberglass:
http://www.jalopyjournal.com/forum/showthread.php?t=380196&highlight=fiberglass+shroud

And here's one made out of kitchen trays that looks really good:


That said, there are lots of ready-made shrouds out there that may work with a little modification: Remember the shroud doesn't know if it is mounted vertical or horizontal. P.71 of the Sachse Rod Shop catalog gives actual shroud dimensions:
http://www.sachserodshop.com/web_cooling systems.pdf

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