For negative G maneuvers the two items to consider is your fuel and your oil. All airplanes can do momentary aerobatics, even with carburated engines. But of course if you're in the maneuver too long, the engine will cough since fuel is no longer getting to the engine, either due to the evacuation of the float bowl or simply because you don't have aerobatic fuel tanks. If you're serious about aerobatics you will most likley have to use a fuel injection system.
To get fuel to the injectors though, you will have to build a fuel tank, usually just a header tank, that the engine can feed off of while the airplane is upside down. This is a special tank that allow a flexible fuel pickup line to stay submerged regardless of attitude.
Regarding the oil system - for normal operation or light short term aerobatics a standard gravity drain system, even a dry sump, is sufficient. It is generally a good idea to provide the external sump with sufficient volume so if an extended negative G maneuver is flown it can supply oil even if the reservoir is for the moment not being refilled. As with the aerobatic fuel tank, a flexible tube or "clunk" is used to keep the oil pick-up always submerged.
For higher performance applications, or if you want better oil system performance, or if your sump is above the crankcase drain point, an evacuation pump will be necessary to pump the pooling oil out of the case and into the sump.
A good dry-sump pump and set-up will vacuum and pressurize the oil in all situations. The LS-7, however, is a 'semi-dry' sump used manly for the 'hard' manuvers most owners will do on the street - ie, less than 1g You can add an 'oil accumulator' to help keep the oil pressureized... you can Google these.
What about sustained inverted. Do they tap the valve covers to remove the oil to the sump?
What is everyone using as the PCM/Computer to run the LS motors, to 15, 20 thousand feet. Does the stock computer have the programming to run that high and cold? What about 2 computers any one run dual computers?
I am excited to go to the EAA air show in Hando in 2 weeks. I have the bug big time to build a Legends P-51.
Most peeps run a slightly modified OEM PCM with the sensors that you will not use programed out, and the fuel/spark/rpm maps modified for sustain higher RPM usage. There are several reprogrammers out there - just tell them what you need. Two can be used in conjunction with the easiest way (for me at least) being a 'A-or-B' switch with diodes isolating the PCMs. Mallory or MSD have a way to connect two, though I believe it functions the same way - only one PCM running at a time.
As for the dry-sump - yes, you would have to tap the block in several places to evacuate and supply the oil correctly. You pretty much have to do this in a full dry-sump application anyway since in a dry-sump, there really is no 'oil pan' per say. The sump pump evacuates the oil in several places, filters it and sends it to a reservoir (holding tank) where the air is release before going back to the pump to be pressurized and supplied to the block. The whole thing works under pressure and vacuum and actually required a fairly 'leak free' and sealed engine. In the LS7, the oil is pressurized going into the block, but is collected in an oil pan before being evacuated. Thus the 'semi-dry' part.