If this is going to be a true street engine I would look at setting up the main bearing clearances on the tighter side. Spent years working around BBC marine engines that were all aluminum. The engines used Donovan aluminum blocks with a 3 inch main bearing for increased strength. The main bearing clearances were set at .0018 due to block growth. We used hydraulic rollers as these were not high RPM engines. 5500 was about max RPM but these engine would spend most of their life in the 4000 RPM range when not at idle. The engines stayed relatively cool since we have an unlimited cooling supply of water. Engines used a closed cooling system with heat exchangers with a normal operating temp of 160 degrees. Also used Mobil 1 15-50 for oil.

With that being said there was a lot of time and testing put into determining what worked best for that particular combination as far as clearances go.