Track use is a very different animal to road use, but if only occasional track then I'd go 2.5 myself.
Standard block is find up to about 450and with the right supporting mods will be fine for odd tracks days.
R3ason for the2.5 is it makes a great road engine, loads of low down grunt.
I have acl race bearings, make piston, Manley rods. Superteck valve kit in version 5 heads and a gt2871r billet turbo. Plus whole heap supporting mods like front mount and 6 speed box. Currently run ing 398bhp and 465ftlb bit eventual target is 500bhp +