if you go the weld and ream route. it would be your best be the right reamer. there's different types of reamers that can take abuse. those reamers are $$ if you want the nice ones that can take the abuse from the welds. my fabricators go through problems like this all the time with drill bits to reamers etc......... I can refer to a brand name called Viking Drill and Tool.
http://www.vikingdrill.com/viking-Product-Catalog.php