If you are looking for a lighter flywheel you don't need to spend all the money for an aluminum one. GM Performance Parts has a 15 lb lightweight wheel for the small block Chevy that is nodular iron. It is available only in the 153 tooth 12 3/4 inch size that takes the 10.4" clutch. You can get it for the earlier engines with a 2 piece rear seal or for the 87 and later jobs with the 1 piece seal and smaller crank flange so be sure to specify the earlier one for your 250.
If your truck now has the 14 inch 168 tooth wheel then you will also be into it for a new clutch & pressure plate as well as a starter and may need to drill and tap the necessary hole for the starter bolt. Some blocks had both sets of holes already tapped. Only you can decide if all that is worth any potentially small gains in performance.
