No. The bolts may line up to actually put the head on, however your horsepower is due to the matching of the piston head with the cylinder head to produce an even flame across the top of the piston. It is important that the radius on the piston matches the radius on the head. The head on the 380 will not match up to the 250 due to the larger piston volume of the 380 vs the 250 or 300.
That is a personal preference. The 300 has more hp and torque and is just a couple of pounds heavier than the 250.
no only a ktm 50 engine will work good for a 3 stroke 380
No, 93-97 ktm 250-360 exc will fit it, not much else. found out the hard way on my 96 ktm 360exc
the engine power and the seat height
yes there is the ktm ktm 85 ktm 110 ktm 125 ktm 150 ktm 250 ktm 500
50:1
800ml
ask at a ktm shop
2009 KTM 250SX retail price $6598
around 44
580
For a 250 SX KTM recommends Motorex Top Speed 4T 15W50 (.7 L). For a 250 SX-F KTM recommends Motorex Power Synt 4T 10W50 (1.1 L).