I take 3H as GF, denying 4+ spades, 5+ clubs, good ♥ stopper and implying ♦ fit (what shall partner do with 3424 or 3334 shape). Anyway small slem is certain (unless we miss 2 keycards) and grand is near.. I´m afraid 4NT rebid could be undestood by partner as quantitative (18-19 bal), so I´m a 4D bidder. Then after 4H or 4S - RKCB, after 5C - 6D, after 5D - pass (partner should cuebid ace if he has any).