1. Buy engine
2. Sell/advertise to someone involved in the European historic racing scene.
3. ????
4. PROFIT!!!
5. Buy 'crate' 302 and restore the rest of your car with the proceeds. True story.
Never. Ever. Buy a crate engine. EVER. Complete waste of money. Most of the times you can get it and build it yourself (or have someone do it) and get more power for at least $5k cheaper. Not worth the extra cost at all. Especially with the cost of shipping.
EDIT:
At the op, if you don't want to build it with performance parts, there is always the option of a stock parts build, which is very mild but will bumpp you up noticably in power. For this though I'd scrap a 289 and get a 351 because 1969 was the best year for that engine. First, you would need to convert the intake to a 4 barrel intake if you find a 2bbl. Mind you, 351W's are easier to find than 289's. You have several options, and for this build:
Any year 351W will do, pre 1974 are the strongest due to the higher nickel content however all 351s are capable of 800+hp on a stock block. So no need to worry about this, but pre 1974 are the best if you ever want to take this further. If you end up with a block after 1974, pretty much everything on them is **** stock. Higher deck height that lowers compression with garbage smog heads etc.
Best OEM parts, some aftermarket:
1969 4bbl intake
Block bored .030
1969 302 Heads (had smaller combustion chambers than later, increase of compression) Make sure you get the valve seats hardend, most shops will know about this. GT40 and GT40P heads from late model 302's and 351W's (late 1990s) are some of the best stock heads available, you can fetch a pair for about $400 and fully ported will net you a good 150+hp increase. Cleveland 2V, 4V, and Aussie 4V heads will give you a Boss engine. These heads fully ported will give you 10:1 compression and higher if permitted (up to 12:1 or more). Premo full would be best. Putting 1969 302 heads will require you to drill the block out so the head bolts will fit due to different sizes. This is not a very common practice (not many know about this) but when put to use it's a very good trick to have on this engine. Really anything is better thatn 1975 and up stock heads.
Longtube headers
Flowmaster exhaust
Holley 650CFM Vaccuum Secondary 4 Barrel Carburetor with Ford A/T Kickdown (if it's automatic transmission, not mandatory)
RV Cam (mild street camshaft)
MSD Ignition (Blaster II)
Accel Plugs/Wires
Wiseco .030 over pistons/small dish
400M Engine Rods
Rockers (roller conversion is a pain in the ass, don't bother with blocks older than 1992)
If you want a forged rotating assembly you can get a lot of power from those as well.
This mild build will bump up a 290hp 351W to about 350-375hp at the wheels and if you add in a few more things you can easily get 450hp out of stock parts.