I think a 570 on a stock 225 may be a little to much, unless you drive it on the highway a lot. It would get less MPG during slower speeds on the street.
I will be upgrading the camshaft putting headers on, electric ignition and putting a offenhouser Intake manifold http://www.summitracing.com/parts/OFY-5270LK
And boring it out a bit when i rebuild it and hottank it