I've got a problem and I hope maybe some of you have some ideas. How do you check out the inside of your fuel tank w/o taking it off the car?

For background info: I've had my Z28 sitting for nearly 4 years and I'm finally getting close to putting it back on the road (long story, ex-wife made some deal to get an engine swap done while I was out of town, only got partially done and I had to figure out how to put it back together again...yadayada). I removed the gas cap (pressure vented out for a while when I took cap off), siphoned out about 4 gallons of gas from the tank (using a 6 ft long siphon hose) and it now "seems" to be empty. However, I'm worried that I might have sludge in the bottom of the tank. I want to avoid taking the tank off if I don't have to do it.

Here's what I've tried so far:
Used a 2ft long boroscope, tried to look inside tank, wasn't long enough to see beyond filler neck.
Checked for sludge/fluid on end of dry siphon hose, came out clean.

Any help would be much appreciated?

 

Here is what I did to drain the tank:

Disconnect fuel line between the fuel pump and the carb. Add about a half gallon of gas to the tank. Attach a hose that you can pinch off with a clip of some kind to the fuel pump. You may have to purchase an adapter. Disconnect the distributor power or remove the cap altogether. Use a clean bucket and put the other end of the hose in the bucket and crank the engine a few times to prime the gas line. The gas will trickle out due to siphoning action and fill the bucket. If it comes out brown, you have sludge. Hopefully it is minor.

Be careful and have a fire extinquisher handy!

Mine was completely rusted after sitting 12 years and I replaced the entire fuel system. Pump $29, Gas tank from the junk yard $50, Gas line $20. Three days under the car with your son, priceless.

 

mnegovan, thanks for the great idea! I'll cross my fingers and hope that it comes out clean.