Michael,
I believe that those valve covers "could be" period Edelbrock or one of the other big names.......I have a set somewhere but couldn't put my hands on them if you gave me another Mangusta!!! (But I'd sure try!!!) The logos look either custom made or modified Pantera versions not the "pork chop" version the Goose typically comes with....
I would also implore you to install a thermostat in the engine. If you've already modified the 90 degree fitting off the front of the intake to accept a t-stat, well then good job!!!!
Without one, you are begging to wear out your engine prematurely. It will never warm up....to proper operating temps! ....OK perhaps not never, but perhaps not as quickly as it should......to get your heater working ASAP for winter driving!!! 
I had a think 3/8" or so piece machined up to fit between the pipe, and the intake. It had the recess carved into it and fit using 2 gaskets and slightly longer bolts to secure it. Worked like a champ! Quick warm ups! NO ONE will ever point it out that it's "not factory"!!!!
Cheers!!!
Steve