Judy Garland backstager “End of the Rainbow” has booked Broadway dates, lining up a spring run that opens in April.The London hit, which stars Tracie Bennett as Garland, has been incrementally laying plans for a Rialto berth for several months. Last spring, an upcoming stint at Minneapolis’ Guthrie Theater (where the show plays Jan. 28-March 11) was labelled a pre-Broadway engagement. Terry Johnson (“La Cage aux Folles”) helms the show, set in London just before a late-’60s series of Garland’s comeback concerts. The play-with-music incorporates a number of Garland standards, sung by Bennett in a performance that won the thesp raves in London, where the show recently wrapped a West End run. Further casting remains to be announced for the American incarnation of “Rainbow,” Peter Quilter’s four-character play that preemed in Sydney in 2005 and has since been seen internationally. Broadway version is produced by Lee Dean, Laurence Myers, Jenny Topper — all three on the producing team of the West End version — and Joey Parnes. “Rainbow” begins Main Stem previews March 19 ahead of an April 3 opening at the a Shubert theater still to determined.