Here's the deal: Skateboard hard goods (decks, wheels, trucks, bearing, etc.) are all standardized. All the products (with few if any exceptions) are compatible: any size Venture truck will fit a Santa Cruz/Flip/Krooked deck, as will Thunders, Indy's, etc. You'll notice that Indy's still have two rows of bolt holes in their base plate; that's a holdover from '80s decks that had different bolt-hole patterns. They just kept it around. Anyway, that's minutiae. Point is, you can put whatever you want together on a board.
While you can ride an 8.5" wide board with, say, Indy 129s -- it will work -- but it's far from ideal. Those trucks have a short axle and are meant for 7.5" to 7.75" wide boards (approximately). If I tried to Smith grind with that setup (wide board, skinny truck), I'd likely end up breaking the board -- I have anger issues -- before I pulled the trick. There just isn't enough room on the truck to do a Smith with such a wide board. Also, when you turn, relative to the width of the board, it's just not going to feel right. I'd venture to guess wheel bite is going to be easier as well, as the concave allows for more clearance the further out your wheel is from the middle of your board.
I skateboard one to four times a week, depending on weather and work. And I have for twenty years. I'll notice this stuff immediately. If you're having fun and starting out, you won't. And there's no point in sinking a lot of money when you don't have to. However, when you upgrade, it's good to know this stuff so that you can make informed purchases. Nothing worse than seeing brand new Indys on a board either too big or too small. You're going about it right. Those Spitfires will work great. Get some Black Panther Abec 3s or China Reds. No point in dropping stupid money on Powell Swiss, but you need something that'll roll. If you want an honest opinion -- of if anyone else on here does -- about what a good setup will be, ask. Occasionally shop folks will recommend shit you don't need, but most are straight shooters. Skateboarding was/is the main focus of my life for twenty years.