Magnum 360 build. (HP/tq?)

Valve lift and intake valve diameter gives exactly squat to enable an intelligent answer. What is the head make and flow numbers. What make is the cam and what are the specs, LSA, 0.050 duration and seat to seat duration?
David Vizard's LSA formula tells that cylinder displacement with that intake valve should start with an LSA of 104°. Of course for a serious race engine, that would be the starting point for testing with a few cams.
What is your valve to piston clearance as tested with modeling clay? Did not do that? No worries. Closest approach is about 15° to 10° BTDC and ATDC. Set the engine at the #1 15° BTDC and put a dial indicator on the #1 exhaust retainer. Rotate the rocker to open the valve carefully until the valve contacts the piston. Try 10° BTDC. Then rotate to 10° ATDC to measure the intake clearance. Then rotate to 15° ATDC. This should tell your minimum clearances and indictate if and by how much you can increase valve lift. IMHO this is a big limiting factor for your engine which is fairly easily remedied if you have adequate valve to piston clearance. Higher ratio rockers will open up the flow. The cam is expensive and requires some teardown to replace. If you start with 1.5:1 rockers, going to 1.6:1 rockers will get your lift up to 0.512". Spring coil bind and seat/open pressure may require a spring change. Also retainer to seal clearance would need to be checked. 0.512" gets you into more modern build spec and will let the heads perform. Stepping up on the intake rockers to 1.65:1 ratio with 1.6:1 on the exhaust would likely give more performance. Intake lift would then be 0.528". This is almost 0.050" more intake lift, probably without having to remove the heads. The engine will become snappier and develop more torque. This can also be done after installing and driving the engine, just easier on the stand.