Well, my 'hack' game uses a 20 level progression with 4e-like math, and while its not exactly HARD to convert things the range of modifiers is smaller and etc, so pretty much every number changes. Lots of things ARE the same, but PCs don't just convert really cleanly. You can get a pretty close approximation with a little bit of sliding numbers around, but...
The goal would be to make the numbers equal essentially to 4e level+7 in terms of to-hit. So a 4th level PC in this clone ought to have a +15 to hit. An 8th level 4e PC with a 20 stat, +2 weapon, and +1 expertise and +3 proficiency = +15 to hit. So if a 4th level PC has a 20 stat(+5), then he simply needs a level*2+ a +2 to make things work. Let's call that +2 to hit proficiency to keep it simple.
I'm just throwing out a 10 level game as an example - it doesn't matter if it is 10 or 100 really as long as the numbers match up to a specific 4e level that's not too hard to figure out from how the game is set up.
One of the major changes I would make is re-jiggering how stacking bonuses would work to heavily favor single attacks over not-single attacks. Basically, you get bonuses to damage from every W/I instead of per attack and every bonus that's not defined as untyped is made into a bonus from the source it comes from - an enhancement bonus to damage is now an item bonus to damage as is Dragonshards and Iron Armbands of Power. So they don't stack, but a +2 weapon with a 5w attack would be +10 damage instead of just +2. Bonuses from class/paragon path are power bonuses, so don't stack with power bonuses from powers. Forced Vulnerability is actually a power bonus to damage.
That would end up speeding up the game because 5w+stat attacks become very competitive with 1w+1w+1w(+stat) attacks. And ridiculous stacking of options just doesn't work, so such a PC might not work in an extremely over-clocked 4e game, but that's a feature IMO.