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Looks like the overdrive is disconnected, does that make a difference?

As Ross mentioned, grinding going into gear is usually a symptom of a clutch not fully releasing or synchros not working.

If the knob is out and cable is able to move the lever so the OD is properly locked up mechanically the overrunning clutch cannot engage because the OD gear train is essentially a solid unit. The car acts like OD is not present and was equipped only with a standard transmission.

If the knob is in so the OD mechanicals are free and gears can rotate individually but the unit is electrically disconnected, the overrunning clutch can come into action and the car will freewheel under certain conditions but will not go into OD. If there is damage to the OD it is possible some grinding could occur but that should happen no matter which forward gear was selected.

Neither condition should be responsible for engine power issues unless somehow the OD has become damaged so that it is permanently engaged mechanically. In that situation there would be a perceived loss of power because the car would always be geared fairly low as regards to final rear axle ratio.

Being permanently in OD is not a likely situation unless the car also will not go into reverse. The OD cannot pass reverse rotation thru the overrunning clutch so when all is normal, if reverse is selected a lockout mechanism will lock the OD gears together. The gear train rotates as a unit, overrunning clutch is locked up and power can pass thru the clutch. When actually in OD a part of that lockout mechanism prevents the trans from being able to shift into reverse.

I have found that with the OD knob pushed in - so as to engage the unit - helps make shifting gears easier. This is due to the free wheeling action of the OD. Of course, free wheeling will not provide engine braking and will make stopping more difficult.

Check your clutch pedal free play, should be no more than 1 inch. If excessive, gear clashing will occur on just about every shift because even as the pedal bottoms out on the toe board, there hasn't been enough travel to fully release the clutch.