Both blocks can be bored to 4.185. NASCAR uses the Bowtie blk. but spend $1,000.00's of dollars preping them.
Carl Hink says the SHP and lil M blk are on sale for the next 3 mos and out of the crate the Dart blks are a better choice. About 3 yrs. ago i bought a Dart lil M blk at a very low price because we bought 4 of them. bored it to 4.155, and put a 4" crank in it with Lonati ProMod rods. Didn't have to grind anywhere on the blk. and used a cheapo 7 qt. trap door pan. I did have to use a small base circle cam, Bullit ground me an .880 B/C cam 4.7 swap with a special grind that i ask for. clearance every where no problems.
JMO
Zip.