Xr4 power head swap

[Clange1731]

So I have a xr4 150 and got another power head to put on. The old one was way past rebuild. The one I got is a 2.5 where the old is a 2.4. What complications am I going to get in to. I know the drive shaft length is different between the two

 

[faztbullet]

If its a older one with 2 piece cowl you will need to replace it with a one piece top cowl and split lower cowl and brackets. Drive shaft length dont matter