Internal temp (if that is what you are asking) depends on how rare, or not, you like your tri. Time depends on cooktemp you select and whether you sear first or at finish.
London Broil is a cooking procedure, not a cut of meat (despite what you see stamped on packages). It means marinating, grilling, then slicing thin against the grain. Flank, top round and cuts from the chuck are most often used for London Broil.
I cook tris to the same level I cook steaks -- medium-rare. See Chris's approach here for an approach. Isusally use a kettle but a similar approach. One Can take the tris to a higher internal before finishing if medium or medium-well is desired.