I saw a thread from back in 2008 (I think) that was titled something like "converting my 2.5t into an R". Well, I actually did that, sort of. I have a 2006 S60 2.5t that is hardly that anymore. It's been a 5 year journey that started with just a few mods and turned into quite a project,... that included a rebuilt motor. If there is still a drawback, it would be the automatic transmission, (though I have toyed with the idea of a MT swap, I just don't have the time or energy). The list includes,... shimmed and resurfaced block, ported and polished cylinder head (intake and exhaust ports, combustion chambers, and gasket matching the manifolds). Upgraded to S60r exhaust manifold, performance valve springs and upgraded intake valves. Put in a 71mm K24 hybrid turbo running 22 psi on a stage 3 Hilton tune. 650cc injectors and a DW300c fuel pump. Dropped in the DO88 intercooler and reworked the intake, and 3" oval exhaust with de-catted downpipe. I had it dyno'd before the methanol and it was putting out 346whp from a front-wheel drive automatic. Not bad. According to my ScanGauge II, I am getting to 60mph in 4.8 seconds.

All that said, it has taken a while to get this done, not to mention the numerous suspension and subframe supporting upgrades. And then for fun, I threw on an AEM meth injection system and tuned for it. It is a super fun car to drive and is truly a custom build while still remaining Volvo at its core. Anyhow, just wanted to throw this on here for fun conversation.

 

The S60s do use the 4C shocks but I suspect your suspension tuning would obsolete that difference anyways

 

Being that mine was the 2.5t, I had the standard shock/strut setup - no 4C. That has all been replaced with Bilstein B8's and HR lowering springs.