Too bad you didn't post earlier as I have already left my shop for my trip to New York and Florida as I have probably 20 cores laying around and about a dozen good carbs...
Sherman and Associates makes a top piece, can be found on eBay for about $90. Sherman Auto Parts LH Inner Front Fender Dart/Swinger/Duster/Valiant/Scamp 67-76; Dart Sport/Demo N 70-76; Barracuda 67-69 - 195-24L-SHE - Restoration Performance
Just found out I have one yesterday, it was in a guage cluster I had in a box. I can take a look at it tomorrow and let you know. You might want to Message me as I tend to forget easily...LOL
I have several sets of those, PM me and I can ship them to you. Please let me know exactly what you need and I will provide pictures to make sure they are right before I ship.