Making an object generator?

I have a minigame server where I was hoping to make a conveyor belt challenge. In the challenge, you run on a conveyor belt with lava blocks with randomly generated sizes being dropped at the beginning of the conveyor belt causing you to have to jump around them to stay on. I have created a conveyor belt, but I have no idea how to make an object that generates a constant flow of lava blocks. Please help!

##Concept

You can think of this the same way you'd think of scripting a tycoon dropper. A constant loop, cloning an object and placing it. Only differences are:

• 1) You can't let the conveyor do the work, it will look messy. Parts must be anchored, positioned, and CFramed in a loop.

• 2) You need to randomize the size, as well as the position.

###Steps

So, step one.. have a while loop constantly clone a part.

Step 2 .. Randomize the size of the part.

Step 3.. Position the part on the conveyor.

Step 4.. CFrame the part in a loop

Step 5.. Destroy the part when you don't need it anymore.

##Code

local part = game.ServerStorage.KillBrick --This is the part template
local conveyor = workspace.Conveyor --This is the conveyor
local spawnPos = conveyor.Spawn --This is the kill bricks' spawn position
local interval = 2; --This is the spawn rate of the kill bricks
local lifetime = 20; --This is how long the kill bricks will exist

--Reference the conveyor's size to determine the kill brick's possible size
local size = conveyor.Size.X

while wait(interval) do  --Step 1
	local c = part:Clone();
	c.Anchored = true;
	--Step 2
	c.Size = Vector3.new(math.random(size),c.Size.Y,math.random(1,5));
	--Step 3
	local dif = size/2 - c.Size.X/2; --Account for side margins
	c.CFrame = spawnPos.CFrame
			 * CFrame.new(math.random(-dif,dif) or 0,0,0);
	c.Parent = workspace;
	spawn(function()
		local _then = tick();
		while wait() do
			c.CFrame = c.CFrame * CFrame.new(0,0,-.5); --Step 4
			local now = tick();
			if (now - _then) > lifetime then
				c:Destroy(); --Step 5
			end
		end
	end)
end

You may see an example of this exact code in action here.