They can be heliarc-filled and re-machined. I was in on saving a Commando head that way, back in the 70's ("My buddy rode my bike home from Texas. He thinks it needs a tune-up"). It takes a *very* good welder -- we thought Dave Kolb was just short of an alchemist.
There was a tiny part of me that really wanted to be able to write at the end of this project that "see, there is such a thing as affordable racing" but that would be wholly ignorant to write--even at this point, and I haven't even hit the track yet!
Good for you Kyle. As DougL said "That head IS nasty!" Hope you continue on & give us all the skinny, step by step. By the way, when you say "I will only have a few weeks between receiving my parts & the 1st event in May", not to crush your enthusiasm, but don't let yourself get down if that doesn't happen. Build enough projects & you soon learn that the 1 thing that can (or ALWAYS does) screw up is the stuff you have to sub out. Good luck Man!
I'll let you in on a secret. One of the delivery trucks dropped off a surprise box earlier this week. I figured Millennium Tech would be shipping all of my engine pieces back together, but the crankshaft is already on the workbench now. This means I can take my time with the bottom end assembly (what I am most nervous about) and all I will be waiting on is the relatively easy cylinder and head.
The heads on my 140 were done about 5 years ago, and I have a spare set of heads on the shelf that I intend to send out and have the seats and valves done just to have a set ready for a future engine build or if this engine ends up needing them again sooner than later. Good 140 heads are hard enough to find that I keep any I can!