Copying a known motor as I said before is a good starting point.
I don't think to many folks are running in the 11s with a $500-800 short block, at least not for too long
Yes I know guys that have run 10s with cast rods too. But to dependably run them at that level for long better rods and good machine work are what Jim and Cliff have had done.
The only difference in expense would be $1400 250 cfm Butler D ports vs $1800 out of the box KRE or E heads flowing 260-280cfm +/- additional porting in the combinations you are describing. Cliff has documented what they did on his car. Intake cast iron-porting time or an RPM, many folks even Jim have had an RPM on at various times.
There are many of us whose detailed combinations are listed here. My old 400 is on Bill Boyles site also, good for 12 teens.
My current "expensive" combination I have described many times and has only one "special" part that was only worth 5hp. 2 bolt YH 455 block and crank, $400 SCAT rods, 0.030 Ross pistons- like most folks using. UD flat tappet hydraulic similar to one Jim's brother Floyd used,only has a 112 LS, installed 107 IC. Plain hydraulic lifters. Mainly 1.65 HS rockers-just like Jim. No line boring,no 4 bolt caps just decked and a torque plate hone.
Now the "exotic" pieces-extra valve springs from an another motor, bare E heads that were KRE CNC ported, KRE supplied stainless 2.11/1.66 valves-same price as the ones for D ports. Used Torker II bought here on PY-cheaper than a new RPM, out of the box Holley 850 DP bought here on PY, jetted one step leaner-cheaper than a Cliff modified Q jet(which I do have one also). An HEI distributor with a total of 38 degrees advance.
The only out of the ordinary piece is 1.8 Crower rockers on the intakes only in place of the HS 1.65s.That was the extra 5hp.
I recently picked up some coated round port headers here on PY that were similar cost to buying D ports and having them coated so don't say alot more expensive headers.
So there you go, other than a little more cost in heads no more expensive to reproduce.
David is a nice guy, met him at a Dallas event years ago and even had a time trial against him