Is your dash a sweep speedo and fuel gauge layout?
If it is, you could cut a piece of aluminum to fit the hole in the dash where the speedo housing fits. The opening in my 70 Chevelle is 16.75 inches wide by 4.25 inches high. A standard 8x18 inch piece of sheet metal is more than big enough to mount to the factory gauge mounting holes. The sweep dash opening can hold two large gauges and four small ones in a staggered layout (similar to the Covan's Classic package):
Two months ago I built a custom dash insert like this for my 70 Chevelle to replace the sweep speedo and fuel gauge. I built a template to fit the opening in the dash and utilizes the original gauge dash mount points.
I wanted it to be different, so I went with the Nordskog digital gauge package DP9255. The digital gauges and speedo sender cost about $500 from Summit but were still cheaper than using six Autometer needle gauges (Speedometer, tachometer, oil pressure, water temperature, fuel level, voltmeter).
Mechanical gauges are often cheaper than electric gauges, which require electrical sending units.
I have seen a lot of posts from Chevelle owners saying they bought the Covan's Classic gauge package.
http://www.covansclassic.com/parts/subcat.php?MC=2
The dash insert prices with gauges and wiring are in the $600 to $900 range. The dash insert without gauges is $250.
You said you want cheap, so Covan's prices might be too high.