SARSEP restatement

[B21]

I have a client that needs to have their SARSEP document restated for PPA 2006. They are currently on an individually designed plan because they are ineligible to use model Form 5305A due to sponsoring another retirement plan. Also, Vanguard (the IRA custodian) doesn't have a pre-approved prototype document. If I restate the plan as an individually designed plan, can it be (or necessary) to submit to the IRS for a determination letter? I noticed on Form 5300 that SARSEP is not listed as a plan type.