[I am 90% sure that 30-06 would have to be the large ring Mauser.]
If you'd like to ratchet that up to, oh say "100% sure", then you can do it with a simple glance at the left side of the action.
If the front receiver ring is even with the left receiver sidewall, it's a Small Ring Mauser - and Yes Virginia, there has been many a .30-06 made on a Small Ring Mauser 98 (cock-on opening) action - which is different than a Small Ring Mauser 93/94/95/96/etc (They cock-on-closing).
If the front ring has a step down to the left receiver wall, IOW it's larger, then it's a Large Ring Mauser.
JMO, but a FI imported FN (generally from the 1970's) , although admittedly a nice & superior rifle, is far from a "classic", and I would think you could most easily get an inexpensive barrel for it from Brownell's or Midway, as long as you pick a chambering that uses the same .30-06 size boltface/case head (no belted mags or .223's, etc).
The existing barrel could also be interestingly rebored/rifled to .35 Whelan, needing no other mods.
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