Not sure how long and how heavy duty the line locks that drag racers use when launching at the tree use?.The description for the 1 i have linked here says it can handle pressure spikes up to 1500psi or maintain constant pressure up to 400psi.

Heres a link to line locks at Jegs in Columbus Ohio.

http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?storeId=10001&catalogId=10002&langId=-1&N=4294965737&Ne=1147708&searchType=KeywordSearch&Ntt=Line+Lock&Ntk=all&Nty=1&D=Line+Lock&Ntx=mode%2Bmatchpartial&Dx=mode%2Bmatchpartial

I also just thought that for what your wanting to do and being on a pulling tractor with left and right brakes,your going to need 2 locks.Locking 1 wheel might be ok for level ground though.Another thing i got to wondering is on say the B&M lock kit shown in the picture,is will it need power to it to stay locked?.Been many years since i was  around the drag racing scene,tractorpulls and Harleys took over for drag racing.Heres a link to a B&M line lock kit for $75.99 at Jegs,picture is of it also

http://www.jegs.com/i/B%26amp%3BM/130/46076/10002/-1

Good luck in your hunt and hope this info helped some, Randy.