i bought an 85 fl350 for 1500. IT is missing the carb and intake. It has spark and Engine has compression and turns over good. What should i do for a carb? can i just order an aftermarket or look for an original? And as far as an intake there no way im shelling out 400 for an air box right now. shouldn't be a problem to make up my own for now correct?

A lot of us run a 38mm carb for a slight bit more power but you won't even notice it.
You can run what ever carb you want as long as it's the same size as original or slightly larger. The issue is going to be the intake.
CO

You can try calling Derek Leland Tisinger (661-747-5796) he is a solid source of many new/used parts for FL350's and probably has everything you need.
He also sells an aftermarket intake that allows you to mount a K&N style air filter. In place of the OEM airbox.
There is also https://oddballorv.com/ for some new aftermarket parts that may help you, these can be pricy though.
Oddball also sells the same aftermarket intake as Derek.
And of course Ebay...

If you get an aftermarket carb don't get a Chinese knockoff. They are almost always more trouble than they are worth.
38mm carb works and is definitely an upgrade but can be a pain to stretch over (and lends to the possibility of ripping) the original intake boot if you have one.
A 35mm PWK Air Striker carb is a good option also.

I was having trouble with the stock carb on my FL350. I took it apart and cleaned it, adjusted float, but still could not get it to run right. I was looking into a rebuild kit, but decided to take a chance on a 34mm carb off Amazon for $35. I popped it on and the thing started right up and has been running excellent. Maybe I got lucky...I dunno.

Understand, I do patronize the Odyssey vendors that support these things, because I think that's important. I've probably spent $1000 in the last year with them. But when you're talking $35 vs. $300...

that's fair, and it is possible to get a good carb from them it is really a coin flip with those things, but more often than not I have had nothing but trouble when I try to save a buck, or if a machine I buy has one on it already, It just won't run right and nothing I can do will get it to run right. Also sometimes the thread size on the jets are different than what they should be, so re-jetting it is a pain/impossible.