[DanEC]

I think I would start with the basics and do a compression test and a leak down test first. The gauges to use for this are not real expensive but you do need an air compressor for the leak down test. That will tell you if you have any ring or valve issues and even if you have any head gasket issues (bubbles in the coolant. The compression test may give some clue as to if you really need to be running race gas or not. Next you can do a simple test for an intake manifold gasket leak with a can of starter fluid or a propane torch by going around all the gasket edges with the engine idling and noting if the engine speed increases while spaying a bit of starter fluid or unlit gas at any location. If all that shows the engine is solid then you may just need to give the thing a good tuning and optimize the carb and timing. Or if it is showing problems then back to finding a builder in your neck of the woods.

You could still switch to a dual quad intake if you want - Keith Craft recommended the Blue Thunder MR intake when he was building my engine but due to using a smooth hood I had to go with a 427 LR intake.

The dual carbs and intake are a sizable investment. If you want authentic restoration appearance carbs they are available (600 cfm) from a couple sources but a pair will run quite a bit. If not so concerned about proper Ford era carbs then there are newer 600 cfm Holley and Quick Fuel carbs that will work fine - although to have them set up by a good engine builder they will end up costing you about the same as the restoration carbs. Good news is the old S&H air cleaners are cheap - but they don't flow much air. The filter they use is basically what a Yugo used. K&N makes a couple different thickness replacement filters that will flow a bit more if you have overhead room but there is no way they won't be restrictive for max power. But then think of all the guys running 500 HP motors with a single carb/K&N in a turkey pan - hard to understand how they can get any power out of that.