Sounds like a decent combo except the heads and gear/tire size.
If you have to buy new heads. Which you do need. I would get some oval port Pro Comps. Ebay $699-750 Just the heads. Then fill them with good valves/springs etc. I use Manley, but If you shop, there are some good valves for decent prices out there (see Competition Products broom sheet). Final cost will be not much more than a well done set of 781-049 irons. Compression loss will be less, 115 cc as opposed to 119-122 , you probably won't notice it. Plus you will be impressed with the results.
I am old school on the tire/gear problem.. Chryslers Ramcharger theory I believe in.
Put the biggest, widest tire that will fit. If it spins let air out. If it hooks too hard,, add air.
Biggest rear gear possible that gets 7200 rpm at the win light..