To keep that cam and use 1.7's you will need huge heads. That combo will run like a dog on the street and really only show its power at the track. Unless of course you can turn 7000rpms on the street. But, to take advantage of that cam with 1.7's the rpms will be high, too high for the stock block to live. You will be getting cap walk with the factory 2-bolt block in no time at pretty much anything over 6000rpms as a general rule of thumb.
But since you seem to be pretty well set in running that large hydro roller with 1.7's you have a couple options.
1: you can keep the track heats and pour money into them. They will need some pretty heavy port work as well as better valve springs. Just find a reputable machine shop near you that you trust, let them open up the heads and upgrade the valve train and you will be fine. But be sure their work is proven first, you can make or break a set of heads depending on what you do to the ports.
2: You can buy a set of Edelbrock Victor heads, or TFS R's or High-ports and get some headers that will work with them. The raised exhaust port is common in the larger cylinder heads as it improves flow capabilities on the exhaust side. You are looking at spending some cash either way.
Why is it that you dont want to change the cam? It would be much cheaper and you could hit 400-450hp with much less cam and be much happier with it on the street. You mentioned that you have a nitrous oxide system for the car. In that case a cam like this with 1.6 rockers would run well with your 306ci motor with track heat heads.
http://store.summitracing.com/partde...5&autoview=sku
You will do what you want, all I can do is offer advise. But if you want to keep that block alive then you will need to change the cam. If you are 100% sold on that cam then get some 1.6 rockers. With that much cam you are really over the track heat capabilities and streetability will suffer. That cam will sound great but so will a much smaller cam if you know what to look for. Dont get hung up in the lift numbers, much like hp numbers bigger sounds better. But for the user its not always the best option. Now, the TFS II cam is also a great choice. But that stage III cam is meant more for race only big headed, high compression, high rpm combinations.
If you like then spend the money to max out those track heat heads and use the stage III cam with 1.7's. But I say you will be much happier going to a smaller cam that you can use with your existing heads. Plus, track heat heads, decent cam & intake, and the nitrous will make way more than enough power to break that stock block.