I installed 850 seats in my 544.

You need to measure the old seats and see if they fit,

You should also measure from the bottom of the seat adjustment rails to the top of the seat cushion - If it is the same or less than your 240, you are good to go, if it is more, not so much.

I unbolted the seat adjustment rails from my 544 and replaced them with a piece of 1/2' plywood as big as would fit.

Then I ground the 4 seat mounts off the 850 seats and had 3' x 1/2' aluminum flat stock welded to the bottom of the base frame.

I found a good place to fit the seat and mounted the bars to the plywood so that none of the fasteners were in conflicting locations,

I then marked any material that I could remove from the plywood without losing strength but that would give foot space to the rear, etc.

I then duplicated the custom shaped plywood with a 1/2' aluminum plate.

I could re-install the PV seats as easy as pie.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa