I thought they might not have a kit listed. Did you ask if they would put one together for you? I think the 352 probably lost its popularity after the 390 arrived.
Unless you have a definite need to rebuild the 352, I suggest you look for a 390. They are plentiful and one built to 68/70 specs can be a real workhorse. My machinist likes them because they usually clean up with only minor machining on the first rebuild.
I had one that had 168,000 miles on it. Got it out of a station wagon. The crank showed no significant wear so it was polished only. The cylinders would have cleaned up at .010 but I had it bored .030 over because the .030 pistons were cheaper.
I'll grant you that was a fluke but two others only needed .010 on the crank and .030 over bore.
BTW, Edelbrock makes a 4 bbl intake for the FE engines. I've seen them on Ebay and at swap meets for less then $100.