l have an 88 chevy silverado that has a very worn out 350 in it. I am trying to decide between the stock 350 with only 210hp, or to spend a couple hundred extra bucks and go for GM is popular 350/290 crate engine, that put is out 290hp. Obviously more power out of the 350/290 would be better, but is it worth it and are there any downsides to it such as less fuel economy? Thank you!

Stay with the stock engine,it will be more reliable.

u may get slightly less gas mileage after all u will have to feed about 80 more horses but u may not even notice the differance. here is the problem u r most likely going to have. that 290 hp 350 is going to breath a bit better than ur stock 350 & the 290 hp will also have a pretty deacently larger cam than the stock so ur original ecm (computor) is going to be rather ticked off with u & what u will probobly get is a very rich condition when it is warm. if u do want to go that way do youself a faver & also call up jet preformance or check online. they will program a new chip that will be set up to work with that 290 is specs. put that in before u first fire that new engine & u will be good to go. plus jet can get u that extra 10 hp to have 300hp easily. & just so u know the durability of that 290hp 350 is just as good as ur oem motor. good luck.

go to edelbrock.com and look at their crate motors