The standard GM crate engine is rated 260 Hp provided you use the recommended manifolds, carb, etc. As mentioned they can be had for about $1400 shipped. You will still need all the accessories which could add another $1000 depending on what your preferences are.
The 290 HP can run more. I have installed several of them and believe it is a good option.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine