Well you can go to head with a 64cc chamber, lots of then in the aftermarket that use a modern Ricardo chamber similar to the Vortec L31 but will use your current intake. Summit, Jegs and others have very decent house brands. You can get these in iron which lets you keep a shim gasket to hold your squish/quench clearance on the pistons you have. You could go to aluminum heads but they will need or at least prefer a composition gasket but the thinnest of these are .026 to 028 inch which is going to open up the squish/quench to .051 to .053, however, all is not lost the slightly diminished Squish/Quench function is more than compensated by the thermal characteristics of aluminum. The GM L98 and LT1/4 ran .078 S/Q clearance with aluminum heads on these engines.
The Ram-Jet cam you sight is simply the old 300 horse 327/350 cam ground as a roller with the lobe centers squeezed together to reduce the LSA. This makes for a rougher, meaner sounding idle but basically leaves you a lopey 300 horse cam. In my opinion the go to flat tappet cam is the Comp XE268H. This cam with modern 64cc chamber heads be they iron or aluminum is an easy 370 to 380 hp engine around 5600 maybe 5800 RPM engine with about 390 to 400 ft lbs of torque around 3500-3700 RPM with a very long and high torque curve on either side of the maximum. This with an unmolsted head just bolt in pretty much standard parts, except for the cam kit, together. Milling the chamber down a little, beefing up the valve train with 7/16ths studs, 1.6 roller rockers, cleaning up the ports, just that kind of stuff makes a 400 plus hp engine that lets you know it’s there with an authoritative idle, but has enough manifold vacuum to run accessories and is just at what is comfy with a stock stall converter. Not that it needs be the comp cam but read the specs and compare to other brands that make similar cams. The Comp, if you go to their site shows about 350 hp or so but they used older (buy Darts current design) SR heads. The new SR heads use, you guessed it, a Vortec chamber. But they mixed this with more than less standard GM porting and they include an exhaust heat crossover just like the original GM heads. EQ and some others are using the, aaah, ahem, Vortec chamber. These days on the circle tracks that require an SR head if your not using these modern Vortec chambered SR heads the best your gonna do is run toward the back of the pack.
What can I say besides the only thing getting better with age is the parts for the SBC. Anyway check out the specs of zero lift duration to .050 duration, getting out the amount of degrees in the ramps between zero and .050 is important as is lift, look at the LSA 110 is about as tight as you can go before the low speed characteristics go totally wonky, this in terms of overlap and where the intake closes is a variable with total durations. A short timed cam with a tight LSA has the lobes twisted together to get more overlap, this can come at the cost of an earlier closing intake depending on which lobes got moved and by how much. These cams like the Ram-Jet are trading overlap for better low speed cylinder trapped pressure, but if your running a carb or TBI rather than timed port injection these type cams do throw mixture out the exhaust, that doesn’t cost power but it is a cost added at fill up time. This is a big reason why I’m not crazy about the R-J cam if your not running sequential, timed injection.
Another way to go at this is with a piston replacement with either D dish or flat tops which improves the burn for any head.