225 slant 6 head rebuild - stock valves - maybe 340 springs ? if i were to check the ones on the head and find that they need replacing can i not stay with stock ones > these 340 are stronger but with all this done to the heads it dosent change geometry - ? like the push rods ? - stock ones or does the machine shop have to calbrate ? - ND THE ROCKER ARMS AND SHAFT ASSEMBLEY - WHAT TO LOOK FOR HERE - I AM SURE THAT VALVE GUIDES AND OTHER COMPONENTS ARE IN ORDER - ITS A DRIVER - NOT FOR RACE - a 3 angle grind - and shaving .100 will raise the compression - in doing so what does all this mean ? - a bit of porting and polishing also ? - just trying to do a good nice job and learning as i go - thanks

If you are doing a full head rebuild, and the head is very high mile:

Your machinist will have to determine if the valves and seats can be reground., he can sometimes shim the valve spring if there is some recession, (if it's too much, he will need to install new inserts or you will need a new head). Guides will probably be needed, if they have never been changed out and they have lots of wear to most of them.

3 angle valve job, and cleaning up the ports would be nice to have, no polishing is really needed unless you are doing it yourself and have the time to complete this, if this is a 1 barrel engine you won't notice much from the polish job, mild porting will help a bit.

340 springs are not needed on a non Hi-po engine...if you are just going with daily driver with a stock cam or one of the .435 lift cams standard springs are fine (going to a .470 lift and 268 duration would need the 340 springs).

If you raise the compression, by milling .100, you will have to mock up the head and check geometry with your push rods, or a "test pushrod" to make sure everything is lined up and the pushrods don't get bent up...physical measuring is always advised because .100 may not get you 9:1.... if you cut .100 and use a felpro gasket...your total cut can be about .07-.08 compared to the original engine and shim gasket, using the new cut and the comp gasket....if it's an early engine, it may need more to get there (that's where measuring the deck height - or difference in the top of the piston at TDC vs. the surface of the block- can be important...), some early 60's engines stock were closer to 7:1 compression, so a .100 cut off the head might bring it up to the 8:1 compression by the book...