Beautiful set. Extraordinarily difficult to complete in nice condition. Some tips from somebody who has been working on this (and upgrading this) for over 20 years now.

1. Buyer Beware: If you are not careful you can end up buying cards that look mint - until you inspect them closer. The big 1971 Topps scam is the "magic markered" corners. Unscrupulous persons color in the frayed corners with black felt tip pen, making the corners initially look clean. Watch for colored edges as well.
2. Buyer Beware II: The slightest amount of wear on the corners and edges are magnified because of the black borders.  Because of this, '71 Topps cards are often trimmed by unscrupulous persons. I owned my #5 Munson for over 10 years thinking it was NM/MT, until I looked closer one day. Making it worse, I purchased the card when I was 15 and spending my (very) hard earned money.
3. The Holy Grail: Anyone who has attempted to put together a nice '71 set knows about #536 Claude Raymond. A Claude Raymond that is centered literally does not exist. Nor does one that is slightly off center. If you are looking for a nice clean set and off centered cards bother you, '71 Topps will drive you to drink. Also make note of:
4. Holy Grail II: Another killer is #5 Thurman Munson. You can find them in lesser condition but because of the popularity of this spectacular card, nice copies will set you back quite a bit. This card is also extraordinarily difficult to find centered.
5. Holy Grail III: Jim Lonborg #577. After Claude Raymond, this is (in my experience) the most difficult card to find centered.
6. Holy Grail IV: Also extraordinarily difficult to find centered: #549 Jim Brewer (an absolute killer),  #287 Mike Fiore (good luck finding a centered one), #114 Billy Conigliaro (you can find an occassional centered one but you have to sift through alot of cards. I have 2 for sale in my store. I suggest you buy one), #173 Gil Garrido (you'll search for years!), #270 Rico Carty (centered Cartys do not exist), Denny Lemaster (obtainable but tough), Denny McLain (scarce regardless of centering - centered examples are psycho killer), #446 Bobby Bolin, #220 Ron Santo, #77 Mike Compton, #17 Billy Sorrell & #145 Bill Singer.  I've probably only scratched the surface.
7. Variations: Some variations that you may know about and some that I've never seen documented but I've discovered... The ugly black line at the top of #515 Carl Morton is not on every card. Very tough to find one but they do exist without the black line; The big black smudge on your #306 Jim Nash card is not a defect, it is a scarce variation (unsmudged Nash cards are easier), Same thing with #552 Buddy Bradford, they come smudged and unsmudged (I'm not sure which is scarcer), A cool variation I discovered is #583 Ron Cook. Most cards show his eyes rolled upward but there are tougher examples of Ron looking directly at you. Same thing with #133 Mickey Lolich. Eyes to the sky and eyes directly at the camera.