A tired old horse and parts interchangability

So I recently acquired an Iver Johnson and its been running like a champ.  Unfortunately it looks to have been run hard and long and Im going to need to give it some TLC.

For starters, the ear on the slide on the drivers side is broken off. Im not sure how its gone through a few hundred rounds that way without a malfunction but it has.  The only Iver Johnson slide i have found is from the early 90's and this carbine appears to be late 70s or early 80s.

Now, this gun is worn.  The bore is nearly smooth so imagine the moving parts.  If I toss another slide of another brand on it am I going to see issues?  Im wondering if I should just throw a whole new bolt and slide at it at the same time. If so, is there one or another thats better?  It will likely be run hard in the future as well.

Secondary question.  The bolt is worn so smooth it looks like it could have been chromed, did anybody hard plate the bolts with chrome or is this just from the wear?

Thanks

Like the old saying..."if it ain't broke, don't fix it". If the gun cycles and shoots, I think all I would do is get a slide and yes, any caliber-30 USGI spec. slide should work. I have discovered the bolt dimensions are slightly different. Sticking a GI bolt in there may affect head-space.  In my case it does. I'd just examine the bolt for excessive wear (whatever that means) and obvious cracks. I would not start investing a lot of $$ in a gun that is that well-worn and can usually be had for under $400. 

You never know about the history of a gun unless you purchased it NIB. We know there were some plated commercial components and guns out there and a plated component could have wound-up on your IJ somewhere along the line. IJ picked-up where Plainfield left off and they also acquired Universal at it's demise. You can see fingerprints of all three of those brand-names in an IJ carbine.

More like a money evaporation switch, but its hella fun LOL