They are available from Scat in a custom. 

Nice Brent I guess Jays heads are working well. Only 10 to 1 making good power. Love the flat tap pet to me nothing sounds better not even a solid roller. Was that cam nitride.

Yes, nitrided cam, EDM tool steel lifters. 

Hate to come in behind Blair's big wampuss cat, but thought I would throw this up here as I think (I could be wrong) it's the first dyno test of Jay's Tunnel Port heads.  Just as a note, no head work was done, the heads were assembled with SI stainless valves and a PAC valve spring package.  No port work.  Factory 1x4 Tunnel Port intake had the floors raised/shaped to match the ports in the heads. 

Performance Summary:
      Cubic Inches:  482        Dyno brand:  Stuska
      Power Adder:   Nope         Where dynoed:  Dale Meers Racing Engines
      Peak Horsepower:  586
      Peak Torque:  561

Horsepower and Torque Curves:


Engine Specifications:
   Block brand, material, finished bore size, other notes:  Robert Pond Motorsports Aluminum
     
   Crankshaft brand, cast or forged, stroke, journal size:  Scat 4340 4.250" Stroke
     
   Connecting Rods brand, material, center to center distance, end sizes, bolts:  Molnar, 6.700

   Piston brand, material (caster, hypereutectic or forged), dish/dome volume, static CR:  Custom Mahle, 42cc dish, ~10:1

   Main Bearings, Rod Bearings, Cam Bearings brand and size:  Calico coated Clevite main/rod bearings, Durabond FP-01 cam bearings

   Piston rings brand, size, other notes:  Mahle, 1mm/1mm/2mm

   Oil Pump, pickup, and drive:  Melling M57HV, Canton pickup, ARP shaft

   Oil pan, windage tray, oil filter adapter:  Canton front road race, no tray, Scott Drake oil filter adapter

   Camshaft brand, type (hyd/solid, flat tappet or roller), lift and duration (adv and @.050"):  Custom Lykins Motorsports solid flat tappet, 266/280 @ .050"

   Lifters brand, type:  Trend tool steel EDM

   Timing chain and timing cover:  Cloyes timing set, Shelby timing cover, Lykins Motorsports adjustable pointer

   Cylinder heads brand, material, port and chamber information:  FE Power Tunnel Port, SE exhaust ports

   Cylinder head flow in cfm at inches of lift (28" H2O pressure drop):  315/180
     
   Flow bench used, location:

   Intake valve brand, head size, stem size:  SI stainless, 2.250"

   Exhaust valve brand, head size, stem size:  SI stainless, 1.750"
   
   Valve springs brand, part number, specs:  PAC

   Retainers and locks brand, part number, specs: PAC

   Rocker arm brand, type (adjustable or non-adj), material, ratio:  T&D Tunnel Port

   Rocker shafts and stands, brand, material:

   Pushrods brand, type, length:  Smith Brothers

   Valve covers, brand, type:  Chrome Pentroof

   Distributor brand, advance curve information:  MSD

   Harmonic balancer brand:  Powerbond

   Water pump brand, type (mechanical or electric):  Edelbrock, also turning alternator

   Intake manifold brand, material, porting information:  Factory 1x4 Tunnel Port

   Carburetor(s) brand, type:  Scott Perkins 850

   Exhaust manifolds or headers brand, type:  Dyno headers

I'd shape that hole with a die grinder and send it.

There's nothing straight about a factory FE block.  Mains are whopper-jawed, cam tunnel is usually whopper-jawed, deck surfaces are not straight/flat.  They're a mess. 

Mainly making these for Pond/BBM blocks for a SOHC configuration.  No holes.  Can also be used to block off oil at the cam so that you can pressurize the oiling system before you start building (check for drill throughs, cracks, etc.)

Let me know if there is any interest. 

10-4

Most tall pentroofs will fit, the thicker cast ones may need to be touch-ground in a few spots. 

You can make most anything fit.  As Rory said, you can always add a valve cover spacer, or sometimes I double up on valve cover gaskets to gain clearance.