Looking at the serial number on the piece of tape, you'll want a Wylie receiver to match the case. You'll also need an XTSP Mk13 trigger for your Mod 5. Good luck with hunting one of those down, I don't think that Tom at XTSP makes those triggers anymore, and now they're quite rare to see (and they currently sell for about $500+).
The $2,000 triggers are the Geissele Mk13 triggers, which were used on the Mod 7's. You need to be very careful with these triggers though, unscrupulous Gunbroker sellers have these Geissele Mk13 triggers available, but they're DRMO triggers that are KNOWN to have issues! But, those sellers won't tell you this, they just want your $2,000. I've probably sold about 2 dozen of these Geissele Mk13 triggers over the past 2 years (helping a friend sell the ones he got from Geissele), and they used to be priced at $2,500 a year or 2 ago. None of the triggers I've sold have been surplus/DRMO, all of them have been new in original packaging and acquired from Geissele.
Additionally, almost all of the triggers that I sold have an "R" laser engraved on the housing, which stands for a revision that Geissele made to these Mk13 triggers. The DRMO Geissele Mk13 triggers being sold by shady Gunbroker dealers don't have this revision, and that's one of the reasons why those triggers had failures and ended up at DRMO in the first place! So, if anyone here is looking to purchase a legit Geissele Mk13 trigger for their Mod 7 build, please make sure that you purchase one that's been acquired from Geissele, is new in original packaging, and has the "R" revision marking on the trigger housing. Don't risk spending $2,000+ on a faulty trigger that might break or fire a chambered round with the safety lever, buy the trigger from a trustworthy source.