Always.  Lifters are a lot taller on a roller.

It gave me a mental picture of the pics you shared recently of your first engine build you looked pretty young 

Yeah, I still make mistakes when I'm old.  That's why I'm as bald as a cue ball.

That fiasco opened my eyes up a little bit.  When you can pull an engine on the dyno to 5500 with .012" (twelve!!!) main bearing clearance, all these guys screaming on the internet, "DON'T NICK A CAM BEARING YOU WILL LOSE ALL YOUR OIL PRESSURE" get a chuckle from me. 

That's why I said an extra .002" cam bearing clearance on one journal for the OP won't hurt anything.

I pulled all the caps off of that engine after I found the leak.  All the crank journals looked perfect, bearings looked perfect, etc.  I pulled the crank out, swapped in new bearings, bore gauged the clearances, put it back together, and dyno'd it again. 

It had been a perfect storm for mistakes.  Either someone had mispackaged a set of bearings, or I had put a set of standard bearings in a .010" box at some point.  In addition, my Mitutoyo bore gauge only goes to .005".  So a multiple of 5 is kinda undetectable. 

Things shape your experience and "rules" over time.  This is one of the reasons why I tell everyone to spin the pump on the stand, listen for odd noises, and know that certain pumps will pretty much always make the same oil pressure on the gauge with the same drill motor spinning it.  Looking back at it, it had "enough" on the gauge, but it didn't have what it should have had.

Gotta watch, because some of them are short and/or won't fit a decent rocker arm.  Some of them kinda look like a SBF valve cover the way they're shaped and they don't fit well.

The Moroso ones are expensive, but they are nicely made and will cover pretty much anything.

I have ran factory rockers at .660" lift and 425 lbs of spring load.   That was with a rules road race engine with REM/cryo rockers. 

No way I'd ever associate a factory rocker with a solid roller.   

You can reuse bearings like that.  If you pop them out 2-3 times, then I would put a drop of green Loctite on them before you drive them in the last time. 

How are you measuring the clearance?  With a micrometer and bore gauge? 

For future reference, if you do another FE, grab an old junk factory cam and cut some cutting grooves in the journals.  It will save you a lot of time on fitment.  None of the aftermarket FE blocks will give you fits on cam bearing installs, but a lot of the factory blocks are just badly out of alignment. 

On my Bob weight Card it just has one entry for Piston & Pins. I wouldn't think the same piston from the same manufacture would be that much different. Jay Brown probably said it best.

You'd be surprised......I've ordered replacement pistons of the same job number and they were 10g different than the previous ones.  I think it just comes down to the particular batch of aluminum that they received in.   

I got that email too.