you'd do good to get an assembly manual, paging thru it will be a valuable education
there are L-shape brackets off the lower cowl where the inners attach at the bottom, awkward to get at, one from under the fender, one from engine side [I seem to remember driver side is hidden behind the clutch pedal arm] .... bolts at the bottom of the fenders too, near where the braces attach, hard to see, especially if rusted and packed with dirt .... also there are a number of bolts at the front that you can only see from in the wheel well, best to have the wheels off - 1 or 2 go into the ends of the top 'spreader' and a couple more into the ends of the bottom splash pan
easy way if you're really gonna work it over is to remove the bolts at the bottom back of the fenders and inners to the cab, then the bolts that hold the rad core support to the frame - take off the bumper and the entire doghouse can be lifted off for separation at your leisure - hood can be unbolted from the firewall and taken with the rest or can be unbolted from the inners and removed first
oh - if 'big bolt' is the one to the inner, cut it if you can without damaging the inner or the bracket - if you can't get it free look inside and some of those brackets were bolted thru the toeboard and can be got free so the bracket comes off with the fenders ... if it's the one at the bottom of the outer fender do it however, you'll likely have to repair the brace at the back of the fender it threads into anyway
Bill
