Making the move to roller lifters...

I'm in the process of building a new 440 short block, and I plan on using a set of Indy-SR heads that I have on the motor that's currently in my car when I'm ready to install. The heads currently have springs for a flat tappet cam that are good for up to a .650" lift.
I know I'm going to have to switch springs and push rods if I make the switch to a roller lifter (either hydraulic or solid), but my question is this: If I go with a set of retro-fit roller lifters do I need any machine work done on the lifter bores? Secondly: If I go with a solid roller lifter what machine work do I need done on the lifter bores (I know that oiling can be a big problem)?
The lifter bores, themselves, measure real good, so there's no oversize bore issues.
Also, other than Comp Cams, who sells hydraulic roller cams? I'm looking for something with a lift greater than .550".
Thanks in advance for any help.

I went to a solid roller and did nothing to the block. This is on a big block.

no mods needed on stock block---if you go solid go with Comp 829-16 it has a solid body no oil issues--do not use a banded lifter --if hyd 440 source has rollers lifters for $299 a set--GREAT deal compared to others that probably get them at the same place--that spring you have is usually a comp 928 if so it could be used with hyd roller depending on installed ht -- if you go with a solid be careful and don't over do it on pressure like you would on a racer--this will keep the rollers on the end of the lifter where they belong--street miles can KILL solid rollers with too much pressure and if you get a solid designed for street use it will have easier ramps and not require so much pressure anyway.

So if there's no machining necessary in order to use solid roller lifters, what's the point/meaning of "retro-fit"?
Also, have any of you used the 440 Source hydraulic roller lifters? I was pro'ly going to go with the Comp lifters, but if I hear good things about the Source's I may change my mind.
Thanks (again) in advance for any help.

Ahhh ...... a topic I was thinking about today. I have two projects going-together that I am considering just this.

But it scares me to no end .... do they have these lifters made fail-safe enough ? .... NOTHING could be worse than having a lifter coming apart and spreading all that metal every where.

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what's the point/meaning of "retro-fit"?

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Retro-fit means you are putting a roller lifter into a block that did not have a roller cam from the factory. The retro-fit lifters have link bars to keep them from rotating. If you get hydraulic lifters or lifters with an oil band then run the oil pump with the manifold off and make sure the oil bands don't get exposed which would cause a loss of oil pressure.