Of course you do. We all do; every last '78-88 GM A/G-body car is simply crying out for five on the floor (preferably with a bench seat). The General didn't much like the idea (though he did build a few with manual transmissions, mostly Saginaw 3-speeds) but everything you need to do the job right is readily available at the junkyard and/or eBay. The internet is truly a wonderful thing; here's an extremely helpful site that looks like it took as much work to create as did the transmission swaps it documents. Good step-by-step description, plenty of helpful photos, and all for free!

Installing a T5 into a 1978-1988 GM A/G Body [garage-scene.com]

So You Want A 4x4 Volvo 245? [internal]