I am planning on putting a small block in my 66 chevelle. I have a 400 2-bolt block now that will need some machine work. Would I be better off/money ahead finding a 4 bolt 400 block or even a 4 bolt 350 block (to make a 383) as a starting point rather than put money into a two bolt 400 block? I am looking for a pump gas street/strip motor that will run well on the street and not be embarrased on the track. Some day may even consider a power adder of some sort if money allows (after the rest of the car/chassis gets its needed TLC. Any thoughts or opinions would be appreciated.

Search and you will find some info...
Don't assume that a 4-bolt block is better than a 2-bolt...

The 400 4-bolt BLOCK is supposedly less-desirable, as the main webs of the block are weaker than a 2-bolt 400 (or a 350, etc)...

2-bolt mains can support more power than you think... Maybe go to main studs instead of bolts, and you could even upgrade to aftermarket 4-bolt caps (have them installed before align-boring the block)...

I think all factory 400 cranks were cast (not really sure), so that can be a bit of a weakness, but again, at moderate performance levels, it might not be an issue...

BUT, I think alot is going to depend on your budget and the rest of your combo (what compression ratio/chamber size do you want and what piston choices do you have for a "400" that will fit those specs...

I think the 400 will be a better choice for more low-end torque (better for getting the car going), but really how much difference given the same general parts choices...

383 is nice, with alot of new pieces, but maybe more than what you 400 will cost. 350 blocks are plenty, and probably within a few hundred dollars of the profit from selling your 400 block, so nothing significant...