I hate to say that Nate is wrong (this is probably the first time and I'll likely be banned from the forum forever), but GMC in line six cylinder engines (228,248,256,270 & 302) have 4 main bearing, not 7. Maybe Nate was thinking of the 230 inch 6 (and its variants) that Chevy first produced in 1962, which is a 7 main bearing engine.
Reference is GMC Maintenance Manual, about 3/4 of the way down the left column.
http://chevy.oldcarmanualproject.com/gmc/5559mm/5559mm360.html
