The 3/8 bars are swappable. The 290 has the same large format bar mount as the other large format Stihl saws. Just make sure that the 290 does not have a 325 bar and sprocket on it. The .325 B&C and rim are common on 290 and 260 saws. I run the same bars on my 066 as my 310 (bigger engine than the 290, but otherwise exactly the same saw).
FYI, all of these Stihl saws (and others not listed) all have the same large format bar mounts: 024/240, 026/260, 261, 029/290, 291, 310, 311, 380, 390, 391, 340, 341, 036/360, 361, 362, 044/440, 441, 046/460, 065/650, 066/660. You can swap 3/8 std bars from one to the other.
Note: if you are going to run an 18 inch bar on a 460 (I did that once on the 460 that I had) swap out the 7 slot rim for an 8 slot rim drive. Reason being that you have so much torque with a bar that size it is just going to waste. Swap torque for chain speed and you will rip though wood that much faster. Also you should re-tune your carb changing bars that are that much different. Your max RPM is going to climb at WOT with less drag.
Also of note: you can run either 0.050 or 0.063 gauge 3/8 B&C on the same rim or spur sprockets, and run either on the large format Stihl saws. Just do not run one gauge bar with the other gauge chain.
Also note that you can swap the crummy 3/8 stock spur sprocket on a 290 with a rim drive drum from a 360. They are the same clutch and brake, so you can order the 360 rim drive kit and pop it on any 290/310/390. I have one on my 310 and it is a sweet setup. Chains last longer and rims are far cheaper to replace than spur sprockets.