Doo yourself a favor and lengthen cooler (radiator and this is most important!) and tunnel to 144 right away - you will need the extra length on low snow days. The rail extensions hold up just fine on hard riding no problem and are allot cheaper and easier than replacing whole skid whether you go 136 or 144. The tunnel extended 144 will allow you to lengthen rails also to 144 if/whenever you want to go that route the only diff is a better ride at 144, but will cost oyu a little more in track $. Also do not forget to gear down a tooth or two on top end.
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