This is tough. I've done many productions of this show since 1973. I could try to help you or I can tell you the truth, which I've decided to do: Large casts don't work hardly ever. There used to be a thread on this show's board called "Large Casts." Everyone who had done with a large cast was either miffed or they said it just plain didn't work. Every production I've done with the 'right' number has worked well. I've done two productions with casts the size of yours and they didn't just not work, they stunk. Here's why:
This is an intimate show, Jesus and his disciples. Each has his own personality and it should be made evident, as in any good production
When you split a character into two or three parts, that part is destroyed, because you can't share a personality among several people, and none has enough lines to establish a personality beyond the most rudimentary phase. Jesus doesn't have enough time to get personal with anyone save John/Judas. The intimacy of the show is lost, and without that intimacy and Jesus one-on-one time with each member, which he uses chiefly for teaching purposes, you don't have Godspell. You have a collection of skits and jokes. All the important stuff is gone.
You wouldn't believe the difference. It's night and day. Directors are tempted to do this with big casts because so many shows do have big casts, and he or she rightly wants to give as many people a chance to be in the show as possible. But for heaven's sake, you destroy Godspell with a big cast. You either divide the parts up, or you keep the core parts and the rest of the cast is just there, and they sing the choral parts. But if you costume right, you have too much color, like eating too much ice cream. A little is good; too much and you wish you hadn't.
I judge the show by how many people I hear weeping during the Crucifixion/Finale, and in the two shows I did with big casts, there was hardly any, because the audience was unable to identify with anyone other than Jesus and John/Judas, and even so, they both lose power in those big casts. With the other productions I've done, there was open sobbing every time.
I'm sorry to say these things, and maybe I shouldn't because it appears your cast is set. Looks like I've shut the barn door after the horse has escaped. But you deserve to know.
The other huge requirement to do this show is to have an absolutely kicking rock and roll band backing you. You can't do it without seasoned musicians. I've attended performances where the pianists were people more at home with traditional shows, and they don't have the feel for this music and can't play it. You can get away with less-than-terrific players if you're doing South Pacific or Oklahoma, and I'm not knocking those shows (I love them both), but Godspell is a special case. People know what rock and roll is supposed to sound like, and this show has some very high-energy songs that demand a band that can kick it. Unless you have seasoned
players, it won't come off like you want it to -- and deserve it to.
And you have to have a Hammond organ (or a Hammond simulator) and a REAL LESLIE ROTATING ORGAN SPEAKER. Listen to the original cast album from the '70's. Prepare Ye, Light of the World, and especially the Finale have that Hammond / Leslie sound, and there's nothing like it. Those songs cannot be done on piano alone with any force and emotion. They were written for the Hammond / Leslie combination. If you're in a big area, or even in a small area really, somebody's going to have one.
In the Finale, the organ is especially necessary because it is a death scene. It's frightening. It's horrible. And it needs the majesty of that organ. Get with the music director and show her / him this post. PM me and I'll talk with them (I'm really a very gentle guy despite all this fire and brimstone). What I'm telling you will make the difference between a cute show and a show that dazzles and wrings emotion out of people they may have not felt in a long time. I know this show backwards and forwards. If you were close I'd do keyboards for you, and for free, as I know what budgets are like. I own this equipment and could do the show with one day's review of the music. If you do something enough times, you get fairly decent at it