My biggest curiosity is Valve train/Cam combos.
I think that applies for most of us.
Stamped rockers usually are ok with a flat tappet hydraulic cam, as most don't have much more that 0.500" lift and the spring pressures are fairly low.
Usually, the failure is that the pushrod breaks through the rocker arm. Really just the strength and material thickness of the stamped pushrod cup in the rocker arm.
I think Mopar Performance used to sell some stamped rockers made of slightly thicker steel?
Stock and most of the entry level aluminum heads use the stock rocker arm offsets. The aluminum race heads usually run a larger offset intake rocker arm.
I think the trick flow heads use a stock offset, but different length rocker arm than stock?
Valve train is usually fairly simple when running under 6,500 RPM with most mild to moderate cam lobe profiles.
High rate of lift solid rollers with 0.700"+ lift, and 7,000+ RPM will require high end valve train parts to survive.
Engine combinations are all over the place, it really depends on application, and what compromises you make.
Example, a Race only engine would normally have very high compression, run 112+ octane race Fuel, have large cross section ports/valves, made for high RPM use, and will need frequent maintenance and parts replacement.
A street daily driver might want a smoother idle, high vacuum for power brakes, good low/mid range torque, low maintenance, use low octane pump gas.
Most of the combinations here will be somewhere in between, from pump gas performance street to (guessing), 10 second bracket 1/4 mile drag race. Usually not too much on endurance racing, but there was a recent post where a member is running the Silver State Classic.
Most recommendations are trying to show best-bang-for-the-buck value.
For me the first decision is cylinder heads. For < 500 HP, stock appearance and such the factory iron heads will work (usually needing hardened exhaust seats for unleaded gas), but depending on their condition might cost quite a bit to rebuild, but likely less than the aluminum heads unless you opt for extensive porting. When looking for the higher end power numbers, larger valve and porting will increase the cost.
Popular upgrades for around 500 HP are the 440 source stealth heads for about $1200 /pair, and they have an outward appearance that resembles the stock iron heads, and 80cc chambers. And The Edelbrock E-Street $1,500 /pair, these can be bought as 75cc version if you need higher compression.
The Edelbrock RPM heads $ 1800+ / pair are 84cc chamber, and common for 500-600+(with porting) HP engines.
I don't know too much about the Speedmaster and Procomp heads, but I hear they are copies of the Edelbrock heads?
The newer Trick Flow 240 head around $2,200 /pair are factory CNC ported and outflow the above heads. These are one of the best bang for the buck heads for 600+ HP, but they do recommend a specific Harlan Sharpe roller rocker arm set that is expensive. Others have used these with other aftermarket roller rockers too?
If you need a small chamber head to boost compression on a lower compression engine, there is the Brodix B1 B/S, 65cc chamber, but likely around $3,000+ pair once assembled and requires offset intak rocker arms (1,180 each bare without valve, springs, etc.)
The above are the most common standard port size / height (work with stock type intakes and valley tray) heads.
The Mopar Stage VI is standard port, but raised runner. I think these might need offset rocker arms too.
The Edelbrock Victor $963 (and Victor Max Wedge) each bare, again likely $3000+ pair assembled, and require offser rocker arms.
The Indy, Victor Max Wedge, Trick flow 270 heads use the larger max wedge intake port sizes. Indy and Victor use offset rockers, and the Trick Flow recommends the HS rocker arms. Expect to spend around $1,000+ on rocker arms for these heads.
All the aftermarket heads use reduced wrench head cylinder head bolts (or studs.) The bolt kits for most of the heads is around $100.
