Ring in the new with some quality time with your old truck! A great time to tackle a winter project. If you do not have access to your truck, start your parts list for spring!
The days are officially getting longer now, you know!
Hy Alex Arrow, In my experience Canadian GMC engines which have serial numbers that begin with the letter "G" as on the serial number plate picture you posted are 248 engines. I believe the fact that your engine only has the numbers 248 indicates that the engine was replaced at some point in the trucks life, hope that helps.
you probably have a Chevy engine, Canadian GMCs in those years come with Chevy engines when new and the truck frame would need to be modified to accept a GMC engine if someone had managed to fine one to put in there
give us a better view of the overall engine or the block casting number, but from what i see in the photos you have a replacement 235 with non factory stamped numbers (number physical size is too small) -stan